1988 escort GT runs rich


Old 03-05-07, 04:56 PM
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1988 escort GT runs rich

1988 Escort GT, 1.9L VIN J, 169,000 miles, wonít pass smog test. It runs rich at idle and fine at cruise. Changed spark plugs, cap, rotor, plug wires, pcv valve, air filter, O2 sensor. Set timing @ 10 BTC with dist. wire unplugged. Fuel pressure with engine off is 40 psi and drops to 35 psi in 30 minutes. Fuel pressure with engine running reads 31 psi at idle and 40 at rev. No gas in pressure regulator vacuum line. I checked EVAC purge valve and it opens when throttle is cracked. Checked for vacuum leaks. Removed and cleaned idle air motor.
I cleared codes and I still get code 42 (rich) with engine running and in memory. I can make it spit out a code 41 (lean) in memory by pulling pcv valve vacuum line off, which kills the engine.
The emissions read HC ppm = 447, should be below 220. CO% = 3.93, should be below 1.2. I donít have a compression tester that will fit down the plug recesses, so no cylinder psi but engine runs strong and smooth when warmed up.
Could the injectors cause this? Should the fuel pressure be lower at idle? Any help or ideas would be appreciated.
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Old 03-05-07, 05:17 PM
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Bad catalytic converter most likely.
Old 03-05-07, 05:59 PM
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Pull the PCV out of the tube and let it breath 'fresh" air..........Vehicle should still run (don't disconnect the hose TO the PCV)........Note changes in HC and CO.........Problem may be as simple as an oil change
Old 03-05-07, 09:57 PM
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do the compression test

buy or borrow the tester
what did the plugs look like?
did they all look the same?
black fluffy stuff around the insulator?
do you have light brown stuff (like coffee w/ cream) on the top of the dipstick?
I had and '85 1/2 escort with the 1.9, but with a carb w/o any feedback (no computer and no 02 sensor) it was a real P.O.S. When they started emissions testing here it never passed. It ran too rich but had no divability problems related to the richness.
I say do the compression test ,because I saw a line of about 30 escorts in a junkyard once, and not a single one had its head. Sombody wanted those heads.
the injectors are probably fine. A 5 psi drop in 30 min is not much. your car is too old to have a o2 sensor after the cat, so a bad cat is not causing your CEL.
Have you jacked w/throttle and/or throttle position sensor? In some older cars, at closed throttle the o2 sensor (one wire) does not control the mix, since it has a chance to cool down below 600 F (?). Later cars have heated o2 sensors. I have heard of bad throttle position sensors or adjustments or adjustments to the closed poition of the throttle causing your problem.
Old 03-06-07, 04:03 PM
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All 4 plugs were sooty black. No signs of oil fouling. This car has a 3 wire heated O2 on it and you’re right, there is no O2 after the cat. I’m going to buy another comp. tester, one that will fit down the plug recesses. I didn’t mess with the TPS but that’s a good idea even if the car it didn’t spit out a code to indicate it to have a problem. No moister in the oil.
Thanks for your input.
Old 03-06-07, 04:17 PM
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pull pcv valve

I pulled the pcv valve and it made no diff. I also pulled a vac cap off and got the code that said MAP sensor out of tolerance and code 42(rich).
Old 03-07-07, 06:42 AM
Join Date: Sep 2004
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gets hot?

make sure t-stat is not stuck open
check resistance at temp sensor for computer (not fan switch and not dash gauge) with stone cold engine and hot engine. Without spec., guess readings should be about 10x different.
Old 03-07-07, 08:18 PM
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Does this engine even have a MAP? (Speed Density)
Or is it the Mass Air?
Old 03-08-07, 03:34 PM
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1988 escort GT runs rich

Yes, it has a map on the pass side strut tower. It must sense atmospheric pressure because it doesnít have a vacuum hose going to it?? I checked the vacuum diagram and no hose to the map sensor. It also has the MASS. If I pull a vacuum cap and run the codes with engine running I get code 22 (MAPP sensor input out of test range) and code 42 (EGO shows system rich). I can force it to read a code 41(EGO shows system lean) by pulling the PCV hose off, so I know the O2 is reading correct?? I also checked stat, Thereís no flow in radiator until engine is worm. Iím going to check the coolant sensor, per Peabees suggestion, as soon as I can get to the junk yard and get a coolant sensor plug to clamp my ohm meter to because that sensor is buried under the intake and between the block and firewall, no way to get probes to it. I did run codes with engine cold to see what coolant sensor would do and got code 21 (ECT sensor input out of test range).
I found the engine to chassis ground strap broken, it looked good but was barely holding!!!! Could it be this simple???? As soon as I replace it Iíll post back.
Keep the ideas coming. I do appreciate your help.
Old 03-09-07, 10:51 AM
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The MAP sensor may be mounted IN the intake manifold (manifold absolute pressure), so you wouldn't necessarily see a vacuum hose, only a wiring connector.

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