1988 350 TBI idles funny, stalls when put in gear, and accels rough...

[irongun324]

Perhaps, but for now it is running very strong. No codes, and no hesitation. Even starts too fast now!

[rfmaster]

Originally Posted by soxplayer

You might have a bad MAP sensor. It is cheap and it is THE main sensor the controls the fuel mixture off idle.

ACDELCO Part # 2131545 {#12569240, 16137039, 16254719, 213356} replaces Delphi 213-185 and goes for about $45. Even though MAP sensor can be damaged by moisture accumulation or engine backfire OE units are robust. Can not say the same for the after market. Out of about 10 GM JY units that I have pulled all checked out OK. Some dirtier than others, but all are functional. A failed MAP sensor will also set SES code 33 (low vacuum, high MAP voltage) or 34 (high vacuum, low MAP voltage) - so before spending money on sensors check your codes.

//RF

[olds4554speed]

I have a fully restored 1991 Chevy Suburban that has fresh engine transmission rear end paint interior and I have left nothing undone or unrefreshed.

About 3 months ago it quit running cold in Houston and had to have it towed back to Dallas.

For all parts below I acquired all parts thru O'Reillys Auto Parts.

Hereth begins the diagnostics, no CHECK ENGINE LIGHT was produced.

Similar issue occured 3 years ago on an older engine ,same truck. At that time it was a bad EGR VALVE. I had bypassed the vacuum source and it ran fine. So I replaced with AC DELCO EGR Valve and that fixed the issue. That was then this is now!!!!!!!!

So isolating the EGR did not fix it this time.
Symptoms are: starts, runs fine, until warmed up and then the engine will lose all power and act as if its starving for fuel.

Starting there the original tank had broken plastic windage tray baffles in it so I replaced the fuel tank with new tank and replaced with a new pump and hanger assy. No change.

Next, took the car to local Chevy Dealer that has several old school techs still working. After running their tests they figured the ECM was failing. So I purchased a reman'd unit thru O'Reillys Auto Parts. Swapped the CAL unit and reinstalled it. No change.

Forget the dealer, they were useless.

Next, read when MAP sensor can cause this similar condition, replaced MAP Sensor. No change.

Next, replaced EGR, EGR sensor. No change.

Next, replaced distributor. I had found traces of surface rust on reluctor on distributor shaft so pickup coil maybe effected. New distributor comes with new ESC electronic unit, pickup coil, cap & rotor, also. No change.

Next, read somewhere that the fuel pressure regulator diaphram if split could cause flooding. rebuilt throttle body unit, rebushed it and boiled it out and added rebuild kit and brand new Borg Warner injectors. No change.

Next, read somewhere that Engine Oil Pressure sender (behind and below the distributor) since it serves and oil pressure guage sender and fuel cutoff switch in case of loss of oil pressure, replace it with new to eliminate that. No change.

Next, read somewhere that bad ground wire on Thermostat housing can cause ECM issues. Checked it, cleaned it off, verfied that contact wanhers are all steel and attract a magnet, reinstall the ground wire. No change.



Next, read somewhere that Engine Coolant Temp Sensor if malfunctioning could cause the ECM to think the engine is at -40 deg F in dflt mode.
This would make the IAC Valve stay or go closed as if engine were in cold start mode. This would cause flooding since the injectors are receiving signals from the ECM that its a cold start so needs little air and lots of fuel.
Replace dhte driver side (left side) Coolant Temp Sensor (1 wire pigtail) unit. No change.
BUT BUT BUT, I forgot that there is a 2nd Temp Sensor (2 wire pigtail) unit mounted very front of intake manifold just to the front of the thermostat housing area. I pulled it and replaced it. BINGO!!!!! Problem resolved.

Now I know why ODBI only lasted a couple of years.

Its all about luck. Yes..... if I had started with the coolant temp sensor first I would have gotten off cheap. But all items replace can potentially cause this symptom.

[Longhorn 70]

I had an issue similar to that with my 89 Jimmy. It would also just die once in a while while idle.....Turned out to be one of the injectors on the throttle body was shorted. The way I found out was kind of a bummer but I found it......

On the way to work one morning at 5 AM it started in on me, sputtering and stalling. It would restart each time it died and run great for a while. Finally I prayed Lord, please help me to find this problem. It is really getting on my nerves. Just then.....it died and wouldn't restart. I cranked for about 5 minutes. No go. The injector had finally fried the power fuse for the injectors. Called AAA and drove another car to work.

Replaced both injectors and the fuse....OFF I GO!! No more issues.

Moral of the true story, be careful what you pray for.

[rfmaster]

OLDS

The fact that you had never seen check engine light on should have been investigated before any parts were replaced. The two wire CTS sensor failure is readily detectable when Pins A & B of ALDL connector are jumpered and functioning SES light would have blinked 12 12 12 15 15 15 - repeating. OBD-1 system was primitive by today's standards, but it does the job even today.

CTS circuit
Short circuit between the two pins will result in DTC 14 which equivalent to coolant temperature sensor signal indicates a temperature of over 275° F for 2 seconds.
Unplugging CTS will result in DTC 15 - coolant temperature sensor signal indicates a temperature colder than -27° F for 30 seconds after the engine has been running for at least 30 seconds.

Service techs failed to verify SES functionality during POST - burnt out light bulb can be misleading! This is the basic check of any EFI system, when turning ignition key into ON position. You simply have to follow this basic troubleshooting flow chart to avoid needless parts replacement.

//RF