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TBI Injectors Worn??


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01-07-04, 05:14 AM   #1  
TBI Injectors Worn??

'89 Suburban, 5.7 TBI 265k miles. Injectors are original.

I guess like any other thing, the injectors can wear. With engine off overnight, when I remove my air filter I am having a strong smell of gasoline. No leaks are present. The engine idles poorly inclosed loop and the exhaust smells rich even on a warm engine. Gas milage is around 12mpg (used to be around 14). The O2 sensor's giving a lean/rich/lean (with a good cross count) read like it should. Has anyone ever come across injectors which are worn to the point that the're spraying to much fuel? What were the symptoms?

 
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01-07-04, 04:38 PM   #2  
If you take a timing light and clamp it on the coil wire you can see if one of the injectors is leaking by running the engine and flashing the light at the gas coming from the injectors if one is leaking you will see drips.Also when you first shut it off watch for drips coming off the injectors.You may also have a bad pressure regulator.Do you have access to a pressure guage that will work on this truck?

 
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01-07-04, 05:22 PM   #3  
Davo's got you on the right track. The O/2's are cross counting because the ecm will compensate some of the excess fuel. What you need to look at is the Block learn and Integrater 128 is ideal. If it if constantly dropping from the time it is started and is below 128 then the computer is trying to overcome a rich situation. If it's holding around 128, then you don't have a rich problem. Check that they don't leak after shutdown and see if you still have a good spray pattern with the timing light.

 
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01-08-04, 05:05 AM   #4  
Fuel pressure is fine.
Seems like the block learn was OK at start-up , but I didn't watch it for a drop after running awhile. The truck idles well in open loop even after warm, but with a rich smell to the exhaust. I'll re-connect my O2 sensor (so I'll get closed loop) and see what the BLM does.
I've looked at the injectors with a timing light on a plug wire, and I didn't see any drips while running. Let me see what I see with the coil wire hooked up. Will that hurt my timing light???
I'll try all of this on Saturday and let you know what I find.

 
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01-08-04, 02:59 PM   #5  
Hooking to the coil wire will not damage your timing light.

 
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01-08-04, 04:38 PM   #6  
No point in looking at block learn if the O/2 is disconnected. That's what controls it.

 
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01-12-04, 05:39 AM   #7  
BLM was 115. Changed injectors and went up to 122.
Idle cleared up, now has some stutter @ > 50mph. Feels like timing problem. Scan is not showing a knock detected. Any suggestions???

 
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01-12-04, 09:57 AM   #8  
Originally posted by dirty dan
BLM was 115. Changed injectors and went up to 122.
Idle cleared up, now has some stutter @ > 50mph. Feels like timing problem. Scan is not showing a knock detected. Any suggestions???
A timing issue isn't going to show up at that speed. What exactly is "stutter"? Is it missing, is it just losing power smoothly. What's it doing?

 
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01-12-04, 10:10 AM   #9  
Sporadic missing, feels kind of like driving into gusty winds.

Problem seems to be spark timing. If I advance the base timing, I loose my good idle and have a good highway run. This is old truck and does not have a crank or cam sensor. It is EST controlled for advance. The ECM is advancing the timing but it seems that it's not advancing far enough.

 
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01-12-04, 01:53 PM   #10  
I still say base timing is not your problem. Your just medicating the real problem. Pull a couple of spark plugs and see what they look like. I'm thinking fouled plugs or bad wires or coil. It seems like the secondary ignition is breaking down under load.

 
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01-12-04, 02:00 PM   #11  
You need to check your plugs and wires.Remove the plugs and look for wiggling black lines on the porcelain running from the tip down to the hex part of the plug.Also since you apparently have a scan tool what is your map reading while this is occuring and before and after.Disconnect the knock sensor and see if it clears up.Spark advance shouldn't case this problem,disconnect the est connector and drive it.Are you sure the high speed problem isn't from the lock up torque convertor?

 
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01-12-04, 03:10 PM   #12  
Plugs and wires are new and routed correctly. Torque converter is new, TCC scans ok. If I set on correct base timing (0 with EST Wire disconnected) I get a great idle and poor high end. If I set the base timing advanced (8-10 deg) I get a great top end and poor idle. Right now to get the best of both worlds, I'm running with the advanced timing and leaving in open loop which gives me a good high RPM and a good idle. My MAP read is good (within GM specs) at idle but I haven't noted it yet at highway speeds. EGR Solenoid is working, coil checks fine, module checks fine, temp sensor is fine, battery voltage and to ECM reads good. ECM quads checked fine. Put my ECM in another burb and it ran like a top. We're all scratching our heads.
I can put back into closed loop easily. If I leave the ignition timing advanced, will it cause a bad read on my MAP?

 
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01-13-04, 05:05 PM   #13  
OK-

MAP on cold engine @ Idle 1.04

MAP on Closed Loop @ 2200 RPM 2.7 Volts / TPS @ 1.39

MAP on Closed Loop @ 2000 RPM 2.16 /TPS @ 1.2

MAP on Closed Loop @ Idle .96 / TPS @ .7

Is this any help for us????

 
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01-16-04, 10:52 AM   #14  
Did you guys quit on me???

 
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01-16-04, 01:15 PM   #15  
Have you ever changed the timing chain yet?Also I would pull the distributor to see if the gear is chewed up.Did you try disconnecting the knock sensor yet?

 
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01-16-04, 07:21 PM   #16  
If the timing chain is original...

....that's where I'd put my money. remove the distributor cap and with a breaker bar turn the crank in one direction til you see the rotor move....the stop and turn the crank in the opposite direction until the rotor moves again. Actually...do this starting with the timing mark lined up on the balancer...this way you'll have to real good indication of the amount of stretch in the chain measured in degrees of rotation. More than few degrees would indicate a stretched condition which retards cam timing...which, in turn, retards ignition timing. A certain amount of this can be "covered up" by advancing the ignition timing. high mileage bow ties are pretty well known for doing this...good luck.

 
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01-17-04, 07:56 AM   #17  
I pulled the distributor about a month ago to change the oil pressure sender. Checked it out good while it was out. The timing chain and cam only have about 30,000 miles on them. I checked valve timing (with vacuum gauge for drop) and it was good. I did just notice that when I put it into closed loop, my volt meter drops (when running) from about 13.8 volts to 13 volts. I'm not 100% sure, but I don't think that should happen. Do you think a bad ground on my ECM cause these problems??

 
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02-11-04, 08:12 AM   #18  
Desi,
Here's the old thread

 
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02-11-04, 10:43 AM   #19  
OH, I didn't realize we were talking about this car. You've had a lot of different opinions on this one. What's the manifold vacuum?
Can you duplicate the problem by power braking? I had one act like that one time that had 1 bad TBI injector and 1 good one. You could see that with the timing light. If you can duplicate the problem in the shop, try spraying carb cleaner down either side of the throttle body.

 
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02-11-04, 10:56 AM   #20  
Injectors have been replaced and really made no difference. I'll have to re-look the vacuum to give the numbers, but it was well within spec.
Explain the Power Braking...

 
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02-11-04, 12:11 PM   #21  
Originally posted by dirty dan
Explain the Power Braking...
Can you duplicate the symptom in the shop by accelerating while holding the brake.

 
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02-23-04, 06:00 AM   #22  
'89 Burb R1500, 3.7 TBI (no AIR emmisions)
OK, got a real scan tool on it this weekend. The only anomaly I can find is in the MAP sensor. The OEM manual says to check the MAP sensor for voltage with ignition on engine off. Voltage should read between 4.5 and 5.2. The you pull 10" (34kpa)vacuum on sensor and the voltage should drop down by 1.5 to 2 volts. Mine does just that. It sounds like a pretty wide voltage range to me.
What we're seeing strange is that the kpa readings on the scan do not coincide with gauge on the vacuum pump. For example when I pull the MAP sensor down to 22" (around 75 kpa) which is where my engine vacuum is at idle, the voltage reported to the ECM goes down to less than 1 volt (which I assume it should do) but the scan tool is only showing the kpa to be 28.
I'm not sure what's causing this to happen. I'm thinking that this is more of a scan tool miscalculation than a MAP sensor error. What do you think? I think the tool was a MasterTech and the mechanic claims it to be a great scanner.
Do any of you know where I can find a chart on what voltage the MAP sensor should be reporting at any given vacuum???

 
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02-23-04, 06:05 AM   #23  
go with the voltage readings...

...as the pressure reading is just a calculation. if the voltage redaing (which is what the ECM cares about) is correct, keep looking...and...under 1 volt to 4.5 volts is normal

 
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02-23-04, 07:09 AM   #24  
All other sensors are reading where they're supposed to be. No knock is showing and the knock self test is working, ECM quads are good. Vacuum is good. Engine runs best in open loop.
I'm at a complete dead end.

 
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02-23-04, 08:26 AM   #25  
you state...

...that the fuel pressure is ok...what was it exactly?

if map was your problem, you'd have it in open or closed loop.

how about the egr? checked it yet? GM has a really good egr functional check?

how about carbon under the throttle body and/or the TB gasket...they were real bad for going to pot...

 
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02-23-04, 09:09 AM   #26  
Only kicker to that is that if I remove MAP Sensor vacuum source (and plug the source) while engine running (closed loop), the idle clears up a bit.


Fuel Pressure is at 13 PSI, GM says 9-13 is OK
EGR is clean and holds up with vacuum, solenoid is new.
Pulled TB when I changed the Injectors. All is clean and has new gasket.

 
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02-23-04, 09:20 AM   #27  
mismatched parts perhaps?

does it have the correct MAP sensor...an MDP will drive one nuts...how about the ECM and Prom...are they correct for that vehicle?

 
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02-23-04, 10:09 AM   #28  
ECM & Prom came with the truck. Ran these in another Burb and it ran great.
Map sensor shaped and mounts like OEM, I can't tell if it's a Delco. That's the reason I'm trying to find the expected values.

 
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02-26-04, 06:50 AM   #29  
OK, couldn't find expected values so replaced MAP Sensor with a new Delco. No change in performance.
Any more ideas before I start parting this vehicle out?

 
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02-26-04, 11:20 AM   #30  
Originally posted by dirty dan
OK, couldn't find expected values so replaced MAP Sensor with a new Delco. No change in performance.
Any more ideas before I start parting this vehicle out?
I assume from your response that you still don't see correct values from your map sensor, even with a new one. That would indicate a wiring problem. I had a Lumina with a problem like that and it turned out to be a problem with the signal return wire back to the computer being pinched under the plenum. I used jumper wires to connect the plug to the MAP sensor so I could disconnect the return wire and read the voltage right out of the MAP. It showed correct readings there. I ran a new wire and all was fine.

PS, the wire had to be snipped at BOTH ends and jumped with a new wire for the computer to read correctly.

 
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02-26-04, 12:38 PM   #31  
I can't find what the expected MAP values are other than the 1.5-2 volt range used for testing @ 34 Kpa (10"). To me it seems like a hell of a spread (10% of voltage range) for a MAP signal.
I checked my results at the ECM connection prior and didn't find anything wrong. Guess I can spend some time on that again this weekend to see if I missed anything.

 
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02-26-04, 01:28 PM   #32  
If your using a scanner, you should be able to apply manual vacuum to the MAP with the key on and see a range from approx 1v to 4.5v with varying vacuum. If you can make it run that range, check for reference voltage to be 5v and ground on the other wire (key on). If that checks out then remove the jumper from the signal return wire and read the voltage directly from the sensor and see if you get a correct reading then.

 
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02-27-04, 06:22 AM   #33  
I'm getting the proper range through the scan tool, so it seems to me that my return signal to the ECM is good. The ground checks good at the sensor. My constant voltage at the sensor is @ 4.9 volts. GM says ok to 5.2 volts.
A new direction...
This is an EST controlled ignition with a knock sensor. There is no cam or crank position sensor. What in the ignition system would keep my timing from advancing far enough at higher (2200) rpms???

 
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02-27-04, 03:03 PM   #34  
Originally posted by dirty dan
This is an EST controlled ignition with a knock sensor. There is no cam or crank position sensor. What in the ignition system would keep my timing from advancing far enough at higher (2200) rpms???
What makes you think you don't have a crank sensor? It either has a distributer or a crank sensor. Some engines have both but i'm not sure about that one. The EST is just to control the amount of advance. The knock sensor tells the computer if the engine starts to ping so it can retard timing. The computer controls the timing through the ignition module.
If you used a vacuum pump on the Map and got good readings but don't get them when then engine is running normal, then you have a vacuum supply problem. Tee a vacuum gauge on the supply to the MAP while running and see if your vacuum is normal. You may just have a vacuum problem.

 
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03-03-04, 11:00 AM   #35  
There are no crank or cam position sensors on the '89 5.7 TBI.
Pick up coil in Dist, Ignition Module, Knock Sensor and EST Module controls the timing. First triggered by the ECM's crank signal.
He who can no longer be named used to insist that base timing on these ALDL models had no affect on performance. (He was dead wrong) The base set is critical for the proper advance curve.

Anyway, I put the burb in the shop yesterday for a ball joint and alignment. Left him a history book on this problem. I'll let you know if he can find anything. He was already scratching his head when I left it!

 
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