Severe Stumble Intermittingly on my 90

[moesvette]

My 90 is getting a severe stumble which feels as though I am getting no fuel every time it happens. Has never had an issue to this point. New injectors, new plugs about 1 year ago, and has run flawlessly up til now. Everytime the stumble happens I see the Check Engine light come on briefly. It simply feels like a fuel delivery issue, and am wondering if the fuel pump could be the culprit? The first several times it did it, I drove for awhile and it stopped doing it and drove fine from the rest of the drive. The last time out was by far the worst, and pretty on and off stumbled until I got it back home. Let it rest and fired up again, idled it at 2500-3000 and never a stumble. I have 35,000 miles on it, and it has always been garage stored. Would it be a good idea to change out Fuel Pump if for no other reason as preventive? It seems as though I have read about many fuel pump issues. Any help/suggestions would be most appreciated.

[Kevin]

Sounds like the same problem I'm having with mine. Have you checked the codes? Mine was code 61, vac leak. I've narrowed it down to a bad check valve or secondary solenoid under the plenum

[moesvette]

No haven't checked the codes yet. I was hoping it wasn't vacuum related. I will pull codes and see what I get.

[Kevin]

pulling the codes is the best place to start, that way we can focus on what's wrong vs just guessing and hoping for the right answer. If it is vacuum it's not a huge deal. Still easy to sort out. Let's hope it's something simple and we can get you up and running again soon.

Has any work been done to the car recently? Does it run better with the key off vs on? Mine runs fine with the key off but stumbles like crazy with the key on.

[Z06scentair]

Make sure the plug wire boots are filled with Di-electric grease. Sounds like an arcing mis-fire.

[Schrade]

Fuel pressure; static, dynamic, and leakdown time. Dynamic with vac supply to FPR on, and off...

Originally Posted by moesvette

My 90 is getting a severe stumble which feels as though I am getting no fuel every time it happens. Has never had an issue to this point. New injectors, new plugs about 1 year ago, and has run flawlessly up til now. Everytime the stumble happens I see the Check Engine light come on briefly. It simply feels like a fuel delivery issue, and am wondering if the fuel pump could be the culprit? The first several times it did it, I drove for awhile and it stopped doing it and drove fine from the rest of the drive. The last time out was by far the worst, and pretty on and off stumbled until I got it back home. Let it rest and fired up again, idled it at 2500-3000 and never a stumble. I have 35,000 miles on it, and it has always been garage stored. Would it be a good idea to change out Fuel Pump if for no other reason as preventive? It seems as though I have read about many fuel pump issues. Any help/suggestions would be most appreciated.

[Kevin]

Originally Posted by Schrade

Fuel pressure; static, dynamic, and leakdown time. Dynamic with vac supply to FPR on, and off...

Lets wait till he pulls the codes and we see what they are.

[moesvette]

Both good points, and I have not tried running it without secondary key in off position. I actually am a little nervous to take it out for a drive after the amount of stumbling I saw before, but it would be worth trying it without the secondary key on. Curious though, how if I have a possible vacuum issue, why it will run for periods of time perfectly and then only intermittingly stumble?

[Schrade]

I suggested that Kevin, since he was thinking of replacing the fuel pump, without checking pressure...

Yeah - codes FIRST (I missed CEL note); OP; codes are in History DTC Hxx Module (1?) [ECM]

Originally Posted by Kevin

Lets wait till he pulls the codes and we see what they are.

[Kevin]

Originally Posted by moesvette

Both good points, and I have not tried running it without secondary key in off position. I actually am a little nervous to take it out for a drive after the amount of stumbling I saw before, but it would be worth trying it without the secondary key on. Curious though, how if I have a possible vacuum issue, why it will run for periods of time perfectly and then only intermittingly stumble?

no idea but mine does the same thing. runs fine cold, soon as it warms up it stumbles and sets a code.