Mitre#136

Duplicate Post here to get more ideas

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 !!!

one reply in a prev. post pointed out the Ignition Module as the possible problem, I agree, does anyone else here agree? (I'm running extremely low on cash by now)

kirk158

I also have the same problem with mine except the car is an 89 2.8 v-6 .......I have also done every thing that you have and the head gaskets and intake gaskets with no luck at all I WISH I could also get this problem fixed.............by the way just recently put on an ignition moduale,and coil

Mitre#136

I checked the spark plugs, and after having received that code 45 (rich exhaust) I noticed the spark plugs were really clean and did not exhibit any signs of having burned rich....Then I changed the ignition module....no fix....I then went back to square one.....Hooked up the Fuel Pressure gauge, ran it through the hood and secured it to the window, wouldn't you know that the pressure was fluctuating once the car was in drive and moving, when the car surges, the pressure really fluctuates, apparently it is possible to get good pressure with the car just idling in the driveway but not when it's driving......It would have been good to know that a month's salary ago......I'm going to replace the fuel pump and hope that it does the trick......thanks for the suggestions...

PurpleHaze92

iTrader: (2)

Hey man, Will you let me know if that does the trick for you, that could be my problem too!

Mitre#136

....Almost Fixed...I did the fuel pump, but since I'm tied up for time and cash, I modded the rear shelf and cut a "door" into the car to access the fuel pump. Somehow, I freaking lost my "lock ring" and now can't install the pump properly....the pressure seems like it's holding a little better, although it still seems to drop, although i'm not sure if it's because of the lack of perfect seal at the fuel tank, or due to a faulty fuel pressure regulator, I had to order the ring online cause no salvage yards around here sell them, so....I'm going to have to be on standby for a couple of days.....I'll let you know.......