Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

problems with 88 s-10


strangel's Avatar
Visiting Guest

Posts: n/a

08-18-03, 10:32 PM   #1  
strangel
problems with 88 s-10

i've got an 88 s10 2.8l v6, and it runs like a dream except for a small
problem. first of all, i have hesitation accelerating from stoplights. also,
when the truck is warmed up, it's hard to start it up - i have to press the
throttle to make it start. after i get it started it stumbles for a moment
and then idles fine. i've used winaldl to take a look at what's going on -
when the idle smooths out seems to be when the iac opens itself more. also,
at idle (and ONLY at idle) the oxygen sensor reads 0.99 (rich). sounds like
an egr problem to me, but i replaced the valve with no effect. i then tried
capping the vacuum before the egr solenoid (completely disabling the egr)
and no luck there either. i don't have much faith in my aftermarket
replacement - is there a way that it could be allowing exhaust gasses in
without any vacuum? i also thought it could be the catalytic converter causing problems but, although it was clogged, replacing it only restored some power at interstate speed, it didn't fix this specific problem. what could be some other causes?


Jim

 
Sponsored Links
Joe_F's Avatar
Visiting Guest

Posts: n/a

08-19-03, 03:50 AM   #2  
Joe_F
Depends on which aftermarket part you bought. I'd go for an AC Delco part.

Chances are, if you plug off the vacuum line and there's no change, the problem may not be the EGR valve. However, the diaphragm may be bad and this is causing some trouble.

However, hard starting in general may be fuel/air/spark related. See my "The Basics" post and use that to guide you the next time it happens.

 
strangel's Avatar
Visiting Guest

Posts: n/a

08-19-03, 10:17 AM   #3  
strangel
Well, when it first started I replaced fuel filter, plugs/cap/rotor/wires/pcv. Plugs looked a bit sooty. Since it runs great as long as it's not at idle (even on the highway) I wouldn't think it would be a fuel issue....unless you think that there may be too much fuel pressure causing it to flood a bit at idle, but not any other time. I didn't think that was possible, that's why I haven't checked for high fuel pressure yet.
As for spark, I did the tuneup (as I said above) and checked the ignition coil as described in the Haynes manual, and it seemed to be fine. I also tried disconnecting each wire, then running the truck - each time I noticed a big difference, so that would lead me to believe that each one's firing.
I also checked all of the vacuum lines, even replaced a few that looked like they were on the way out. It didn't help.
Overall the truck seems to need more air at idle. The only way I can think that would be the case is if it were getting too much fuel or if something else (exhaust) were choking the combustion. The reason I say this is because unless i have the accelerator pressed (which means the butterfly valve is open, letting in more air), it won't restart, and then it doesn't want to stay running until the IAC adjusts and lets in much more air than usual. Not to mention the funky smell because of improperly burned fuel.

I hope I haven't left out anything else you need to know.

 
Joe_F's Avatar
Visiting Guest

Posts: n/a

08-19-03, 10:49 AM   #4  
Joe_F
A way to start is to test the various sensors. This can be done with a good DVOM and the proper repair information. It could be an out of whack IAC, a bad MAP, etc, but it's important to test before you replace .

Throw the Haynes manual out---it's useless for most serious repairs. Spend the money and get an Alldata.com subscription or get a GM shop manual. Far superior.

 
strangel's Avatar
Visiting Guest

Posts: n/a

08-19-03, 11:10 AM   #5  
strangel
I've checked the output of all the sensors using WinALDL, and they looked fine. Also, I put it in the shop at one point and they double checked all of the sensors using a DVOM. They also checked all of the grounds. They all seem to be in order. I took out the IAC and cleaned the orifice well...then ended up replacing it because my friend tightened it too tightly when we were putting it back on The new valve behaves the same as the old one though.
I'd noticed oil leaking from the gasket just below the TBI, so that's why it was in the shop - they verified the gasket was bad, replaced it, and when it didn't fix the problem is when they tested all the sensors. They also checked the timing at that time and said it was fine. He also ruled out the injectors and the computer. I checked the fuel pressure regulator later (got a diaphragm kit) and it was fine, so I didn't replace the diaphragm.
Sorry that I'm not getting you all the info you need - this has been an off-and-on project all summer, so I tend to forget some of the things that have been done to it.

 
Joe_F's Avatar
Visiting Guest

Posts: n/a

08-19-03, 11:20 AM   #6  
Joe_F
Check your fuel pressure. It sounds like the only thing that hasn't been verified. Tell us what you find.

You may have to run around with the fuel pressure gauge taped to the window to see what it does.

 
bejay's Avatar
Member

Join Date: Dec 2001
Posts: 2,538

08-19-03, 05:25 PM   #7  
you might check your vacum to your map sensor as i have seen this port on the throttlebody clog many times causing a hesitation the sensor will still be reading even though there is no noticable vacum or very little vacum to be felt on the map sensor hose this causes the map sensor to not increase voltage soon enough when the vehicle is accelerated. causing the vehicle to lean out.

 
strangel's Avatar
Visiting Guest

Posts: n/a

08-19-03, 08:09 PM   #8  
strangel
but the map sensor causing it to lean out doesn't explain why the oxygen sensor thinks it's rich at idle and why it's hard to start once it's warmed up. as soon as i get a chance i'm going to test the fuel pressure, but have to buy a gauge first. any suggestions on which gauge to buy? (cheaper the better, as always).

Jim

 
bejay's Avatar
Member

Join Date: Dec 2001
Posts: 2,538

08-19-03, 08:34 PM   #9  
no it doesnt i just suggest checking it to see if it is causing the hesitation, for all i know the vehicle has multiple problems and may have more than one thing wrong with it.
you say the o2 sesnor was reading rich at idle was this when it was in closed loop on a warm engine? do you get a code 45 rich exhaust out of the computer?
if it wasnt in closed loop the o2 reading is irrelevant, if in closed loop and always reading rich could be alot of things even just needing the oil changed, try pulling the pcv valve out and letting it breath fresh air instead of the crankase vapors if it now switches between rich and lean you probably just need an oil change especially if it hasnt been done since your convertor was replaced.
see if you can rent a pressure guage at your local parts store that would be the cheapest route.

 
strangel's Avatar
Visiting Guest

Posts: n/a

08-27-03, 11:27 PM   #10  
strangel
The rich reading was in closed loop w/engine at operating temp. No code, though. I'd thought of the PCV idea, I'll try that soon as well. Haven't had time to mess with it lately though because classes just started up again

 
Joe_F's Avatar
Visiting Guest

Posts: n/a

08-28-03, 03:53 AM   #11  
Joe_F
Original poster:

Verify EVERYTHING told to ya here. One problem may cause the next. For instance, a MAP sensor problem may fool the computer into making changes in other areas.

I have seen the strangest things cause other problems, so check, check check.

 
bigguy05641's Avatar
Member

Join Date: Aug 2003
Posts: 472

08-28-03, 06:55 AM   #12  
I SECOND THE ADVISE ABOUT THE RESTRICTED MAP SENSOR VACUUM HOSE. AN OLD RIG LIKE THAT, THE THROTTLE BODY PORT IS MOST LIKELY ALL COKED UP. ALSO , DON'T GET TOO HUNG UP ON O2 VOLTAGE READINGS AT IDLE, SINCE THAT RIG DOESN'T HAVE A HEATED O2 SENSOR, IT PROBABLY GOING INTO OPEN LOOP ANYWAYS, WHERE YOUR 02 SENSOR INDICATIONS ARE NOT ONLY IGNORED BY THE PCM, BUT ARE NOT ACCURATE...
IT MIGHT ALSO BE HELPFUL TO KNOW WHAT THE 02 READINGS ARE WITH THE SENSOR UNPLUGGED, IT SHOULD BE AT AROUND 350 MV. IF ITS HIGH LIKE AT AROUND 900 MV, YOU MIGHT HAVE SOME VOLTAGE LEAKING INTO THE CIRCUIT, LIKE FROM A BATTERY FEED WIRE IN AN ADJACENT TERMINAL IN A CONNECTOR SOMEWHERE.

 
Search this Thread