My until now very healthy car is sick.

Symptoms are between 2500rpm and up, and especially bad at 4k-4500 rpm my car is missing, surging, hesitating, not sure the best term. Seems to happen in any gear at least the first 4 and worst in 2nd with more throttle. If I drive like a grandpa keeping the rpms down around 2k no issues at all. No problem under idle or free reving the car.

The first 10 minutes or so the car runs perfect, but after that once I get into the throttle and upper rpm's the car just starts bucking repeatedly like it can't go any faster a couple times a second. I notice a bit of an extra cackle/pop in my exhuast too. With less gas it feels more like a surge. Occasionally it wont happen if I go wot. No SES light either.

I have read many threads today trying to get some good direction and possible culprits. Seems Opti is the leader as always, possibly coil or wires, fuel system

Today I ordered a OBD1 cable so I can get a scan for some guru's to look at. Should have this by Friday.

I just cleaned the MAF which was pretty dirty, but no help.

From what I have read it could be a fuel issue, so I need to check fuel pressure?

My Opti is original, the ignition components(MSD, coil, wires) are about 3.5 years old with approximately 50k on them. Been about 2 years since I changed the fuel filter, and plugs.

I would like to handle this on my own, with some help of course, and am open to suggestions on easy stuff to check. This is my daily driver, so for now I am thankful that I can just seem to baby it along and be fine.

 

Yes, check the fuel pressure. Change your fuel filter, its a regular maintenance job that is regularly skipped. Your symptoms do sound like the opti, I would perform the opti and spark test. Since its original, it won't hurt to swap it out, it would be good maintenance even if it wasn't bad. Have the coil and ICM tested. My money is on the opti, get an AC Delco. Good luck.

http://shbox.com/1/4th_gen_tech2.html#opti_test
http://shbox.com/1/coil_testing.jpg
http://shbox.com/1/4th_gen_tech2.htm...essure_testing

 

I have a similar problem but only when cruising...under 2000rpm i stumble and hesitate...when i punch it or just push it down a little more its fine. Its not my opti...i have an all new plugs, wires, and opti...so what could it be.

 

General question about the opti though. If that was the problem why would it only malfunction after 15-20 minutes of driving? I would think it would be an all the time thing. I drove it this morning to work about 20 minutes trying to get it to mess up and could not do it. Same with yesterday morning. But on the way home or on test drives it seems to happen after about 15 minutes.

 

That's why I suggested to test your coil and ICM as well. A bad ICM usually fails after it gets hot. Forgot to ask, is there any codes?

 

No SES light but I have to wait untill today or tomorrow for my OBD1 cable to arrive to plug er in.

 

Check your fuel pressure and swap out your fuel filter.

 

I will post here as I get results for anyone willing to chime in.

Today to and from work I could not get it to show the stumble. About 20 minutes each way mixed street and hwy. It was a bit cooler today 30's morning and high 50s this evening.

I got my aldl cable and my only fault is a 32 EGR System Fault. Any possible correlation?

Tomorrow I will drive the thing till i have the stumble and figure out how to post the log. Maybe do fuel filter and check the pressure time permitting.

 

funny, I have the same problem! I thought of swapping out the EGR, as I get that code once in a while. Try checking your plug wires? I found that mine were cooked by the heat, and replaced them. It seemed that the problem was gone for a short bit but now is back! I'm gonna try an OTVC setup..

i also have replaced the icm

 

There must be four of us who have this exact same problem. I replaced my fuel filter, cleaned my MAF, all to no avail. The only thing that helped was when I cleaned my EGR it ran better for about a week, but it came back. I just bought another EGR of the boards to see if that might help. Keep us updated.

 

So what was the problem?

 

Ok I started out with having a check engine light, and severe surging, the car was so bad I couldn't hardly drive it a block! I replaced the opti spark (toasted rotor, and bad bearing) With a MSD pro bullet unit, I also replaced the coil with a msd blaster unit, installed accel plugs, and new bosch wires. This made a huge difference, and I could now drive the car, but I still had an SES light, I had the car scanned, and the MAP sensor was bad so I replaced it, the SES light went out, and again the car seemed to run much better! Now my only problem is that when the car is cold, and you try to accelerate from 900 rpms to about 2500 rpms its like the car is dead, and I hear popping out the exhaust (not backfiring) If I get on it like I am being chased by some one, then it bucks ounce, and then it is fine! Also ounce the car is hot, then if I shut it off for a minute or two fire it back up, and try to accelerate it does the same thing!

 

I had a similar problem when I had my MSD coil installed. I replaced the coil with teh stock peice and problem solved. Cant hurt to try.

 

Replacing my opti with an ebay one fixed my issue. It progressively got worse as the car got hotter.

 

ok Thank I may try and replave the coil with my factory one if can find it laying around some where! I have to first fix my clutch issues, and steering..lol