Richgreenster

I pulled my car out to state and Im the car today but as I drove the car to my dealership the car would sputter and backfire at 3000rpm and above. What should I check for?
Here is some info on the car.
1987
vitesse MAF
SMT6
New bosch ho pump with new filter
battery was dead.
Ref. sensors were taken out and reinstalled.

schip43

TB to hard pipe coupler hose is the first thing I would look at, if it will hold speed fine if you step on the gas very softly but falls to pieces if you accelerate hard it's a boost leak.

fast951

Also check TPS

Richgreenster

I can floor it and have it build boost to about 7 psi and it will run just fine, but when it hits 3000 rpm it sputters and back fires.
If I run it in 5th gear on the freeway with no boost, again it will run just fine until it hits 3000 rpm.
I have to jump my battery right now and think that It may be bad. I am checking that right now.

BTW John, It is amazing how smooth the car is at idle and lower rpms with the big injectors I got from you.

Bill

Mine has been doing the same thing for a while now. RPM's hit 3000 rpm and the engine stumbles for 200 rpm then back on power. I have been pulling my hair out trying to find this issue. Put in new tps. Installed known good MAF sensor in place of mine. Installed known good ECM in place of mine. Pressure tested intake track for vacuum leak. New plugs. Injectors rebuilt. Tied fuel pressure gauge into fuel line and taped gauge to windshield, drove and watched fuel pressure. I now suspect my ARC2 piggyback fuel controller. Crazy. If you find your problem, please post the fix. Until then I will keep trying to fix.

fast951

If you have the V-FLEX, check the PB to make sure you do not have the REV limit set to 3000RPM.
Or you may have something else set via the PB which triggers the ECU to shut down.

Richgreenster

I am planning on tunning my car from idle at 14:1 AFR down to 11:1 on full boost. Where do most of you take this reading from? At the tail pipe after the cat or before? I think that my car is running lean and is sputtering from lack of fuel.

Bri Bro

idle =14.7 with ditter
boost = high 11s. Max power is at 12.2 but you want to run a bit rich for safety.

All WB O2 reading should be made after the turbo and before the cat. You can weld on a bung and cap it after you are done.

schip43

Does he have a wide band?

Richgreenster

I have Fabspeed exhaust on it with a Wide band.. I just hooked up a computer to my SMT6 to see if I had any setting in the powerperfect that would cause it to cut out. I did not see anything but noticed that it is running at 14:1 AFR almost constant. This is only reving the motor while in my shop, but still that seems vary lean to me. I need to hook up my wide band to see what is really going on. I will keep you guys posted.

Scott H

At no load and in open loop it should be around 14:1. The turbo can't produce boost just revving the engine in the garage, you need to place a load on the engine. Same reason you see such a difference in dyno plots when doing the runs in 3rd vs. 4th.

fast951

Is this something that just started recently?

schip43

14.7 is what you want at idle and PT. Maybe you have a basic ignition problem?

Chris White

Clearly the only solution is to convert to a 16v head and up the displacement…….Just kidding!

Stick with John, he will help you out. His stuff works nicely – most likely you have a sensor/wire issue and John has trouble shot many of those, follow his advice closely! (I would have guessed TPS also)

Ronin-951

Buy a NEW battery FIRST.