Need help with sputtering when hot

[cburke23]

Ok guys need some help here. Have a 1990 Plymouth Laser 4G63 Turbo, 16G turbo, mainly stock, bigger fuel pump, that's about it.

The car was driving fine, very strong!!! But then when it wormed up to it's normal driving tempter it started to sputter. You could somewhat drive through it but it does not stop. I pulled the plugs and one was as white as paper, the others were fine. My boost gauge also seems to be sitting at 15 not 20 at idle. I have not yet had time to do a boost leak test yet, but I think it's something else anyway. Like I said, It runs strong until it worms up and then it sputters.

Like last night I drove it to the store, boosting about 12psi, ran great, but when I got out of the store and drove it home it started sputtering again.

I just kind of need some ideas so I no where to look. Think it may be the injectors? It would have to be something that works fine till it heats up.

Thanks for any help
Rep points give for help.

 

[95blackGsTurbo]

What plugs are you running? Should be using NGK BPR6ES gapped at .028"-.031". Also do a boost leak test. Always number one on your lists. You can get the injectors flow tested but you have to send them out. You can check resistance between them for irregularites but it really won't help much. Also check your o2 sensor to make sure it is operating properly.

 

[WeaselHack]

Cheek your base timing. Make sure its set to +5 TDC. If its - or + 5 TDC too much it will sputter like you describe. Incorrect timing could also explain your low vacuum at idle.

If that doesn't pan out I would suggest checking for boost/vacuum leaks.

 

[cburke23]

Just did the timing. It's fine, and it only sputters when heated up. I don't think that would have anything to do with timing.

NGK BPR6ES gapped at .028"-.031". Got that.

 

[95blackGsTurbo]

Check your o2 sensor voltage. It could be going bad but you don't realize it until the car goes into open loop.

 

[cburke23]

ok,

I'll do that, do you know what the volts should be by chance?
It's funny but I have never had a car's O2 make it do this. I mean, usally when one goes bad you get bad gas milege but not sputtering.

 

[andymoraitis]

Vacuum at idle is way too low for your altitude and mods. I'd warm the motor and start spraying the vacuum lines down with carb and choke cleaner. If the idle changes, the line needs to be replaced. Pay special attention to the EGR lines as well since these are often neglected.

I'd also like you to verify that the marks on the cam gears line up at TDC just to rule out a valve timing issue.

Check your o2 sensor voltage. It could be going bad but you don't realize it until the car goes into open loop.

Actually, it would affect closed loop more since the O2 isn't used at WOT. I do agree that it would be a good idea to check it though and see if it's failing. O2 readings from a log would be the best option.

Keep us posted,

Andy

 

[95blackGsTurbo]

Yeah I didn't know if it was closed or open loop. Can never remember.

 

[cburke23]

Cool guys, great info. I am maybe thinking I could have a vac leak at the fuel injector, just with #2 being so white. I know the o-ring gets hard over time.

 

[TheCoryMiller]

Sorry for the jack, but I'm using my buddies account. What other things could we look at for sputtering and a 'boxer' sound? The car acts like its not getting power. The plugs are newish, and clean. Ima get him to check for vac leaks and change the o2 sensors, but what else? Maybe the idle control valve? What tests could we use? Thank you fellas. And sorry if this is not acceptable, I'm new to the 4g63 forums.

 

[o0GuitarKid0o]

did you ever find the source to the problem? i ask because im running super rich need to swap to 240cc injectors since its not turbod anymore just need to get my delete plug for the resister pack so i can install the saturated injectors,fpr what else could cause this to happen? very annoyeing waiting in rush hr as it is this just makes it that much more fun...