Mitre#136

88 Pont T/A 5.0 TPI (F)....Ive been having this problem for the last eight months.....The car sits overnight and turns right over and runs smoothly and great until 10 minutes into the trip, then it starts to surge, whether you are at a stop light, or going 60 on the highway. Usually the SES light will come on like a minute after it starts to surge and pull, then the car will run smoothly again, except with a slightly higher idle, but still at less than 1KRPM. Once the engine has been turned off for a period of time and then turned back on, (like once you are leaving the store which you drove to), the engine feels real sluggish and feels like the timing is off and sounds like it's misfiring. Turning the car off and back on will make it run normally (until it starts surging once the engine gets fully warm again) But turning the car off an on again will make it run good, at least for another while.....So far in attempting to diagnose and repair I have:

Replaced IAC Valve
Replaced TPS and adjusted to .55V
Verify Fuel Press. within spec.
Replaced Fuel Filter
Replaced plastic Vacuum lines
Replaced Spark Plug Wires
Replaced Dist Cap & Rotor
Replaced Ignition Coil
Overhauled Fuel Rail (due to leaky injectors)
Inspected/ Cleaned EGR Valve
Got Actron SuperScanner model CP9145 w/ GM OBDI cables (received connection error) followed troubleshooting via scanner manual no avail,
Replaced ECM
Replaced MAF power/ burn-off relays
Replaced MAF sensor
(then found out through more searching here that ACTRON CP9145 has a known issue communicating with ECM's on vehicles "of this vintage" as they put it, currently working on exchange or refund)

After having done all this the car runs much much better than it did when I bought it, but it still acts goofy like this and I can't figure out why, I do notice that the timing seems to change when it surges and misfires, I have to admit that I have not checked the spark plugs because it always tears up my hands, but i'll be replacing those today in the evening. Would it be a good idea to replace the Ignition Module and check the Distributor shaft. I'm open to any and all suggestions, and all the searching i've done has been fruitless.....Please help me I'm going !!!

rhomanski

It sounds like it could be the distributor module.You could also look at the coolent temp sensor and the oxygen sensor.

Mitre#136

I changed spark plugs and ignition module coolant temp sensor to no avail, back to square 1, tested fuel pressure with car in drive and moving, found low fluctuating pressure, need to replace fuel pump.......

raptor80dad

I had a similar problem w/my iroc & unplugged the MAF sensor and solved the problem . MAF was new when I got the car but didnt last long .Replaced it no problem since.

I tested my fuel pressure when it was idling it read 43 psi .Never tested under load so dont know what it should read there .

goodluck


Never threw a code either . mechanic told me to try the MAF