# Car runs rough



## papereater (Sep 16, 2016)

People,

1987 sunbird GT. When I accelerate with much vigor car runs great, no stumbling, bucking, etc. BUT if I say, reach a velocity and want to continue at that velocity with gas pedal at a steady cruising rate (very gentle application of gas, enough to cruise) car kicks/bucks/vibrates like mad. 

I tried a test- floor the pedal to accelerate as fast/vigorously as possible and safely, up to the speed limit, car flies like new. Again, cruise along and car goes back into convulsions. No trouble codes are showing. But I do consume a qt of oil every 1000 miles. And the O2 sensor does not like that. Just replaced it about a year ago. 

Hate to just start replacing good parts. I also checked for vacuum leaks, none found. Open throttle, car is good. Low throttle, high vac (such as idle, slow acceleration, cruising) car is bad. Ideas anybody?


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## Gcraay (Nov 29, 2021)

Pull the plugs and see if they’re oil fouled. Sounds like you’re burning oil. You could have a cylinder out. high speed doesn’t allow you to feel the miss as easily. Bad wires? Distributor?


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## chandler48 (Jun 5, 2017)

Was '87 before injectors? If it wasn't, I'd definitely check injectors, plugs and other ignition parts They could be breaking down with added power applied.


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## Steve2444 (Sep 28, 2020)

chandler48 said:


> Was '87 before injectors? If it wasn't, I'd definitely check injectors, plugs and other ignition parts They could be breaking down with added power applied.


Not sure, GM around that time installed carbs and as an option had carbs with a fuel injection feed over the barrels.
I forget what that pos was called.


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## chandler48 (Jun 5, 2017)

Yeah, throttle body injection. Two injectors for each bank. I had an 86 Nissan Hardbody, V6 and it had it. Still could use some cleaning.


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## Steve2444 (Sep 28, 2020)

Yes TBI that was it.


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## Steve2444 (Sep 28, 2020)

So it may be a straight carb or a TBI


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## Steve2444 (Sep 28, 2020)

It's been a long time since I worked on that vintage, but I'm thinking with that issue and the oil usage it may be the pcv valve.


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## SW Dweller (Jan 6, 2021)

Spark and fuel issues. Either or both. When was the last time the air filter was changed? 
Do you use carb/injector cleaner EVER? 
I would start with carb/injector cleaner, air filter, then the plugs.


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## SeniorSitizen (Sep 10, 2012)

A Vacuum leak is more distinguishable at idle than high speed . If plug wires can be pulled one at a time a vac leak will tell you which cyl. cyls .is / are being affected . Leaking at the correct location 2 cylinders can be affected .

To me this seems to be more of a fuel problem .


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## Domo (Nov 9, 2018)

Spark plug wires and how they are routed.


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## FM3 (Aug 12, 2019)

If it runs great at full throttle, I'd be surprised if it's plugs, wires, air filter, etc. Sounds like a sensor problem that hasn't gotten bad enough to trip the check engine light yet. 

If the car runs well at part throttle when cold, before the engine temp gets going, that's another sign it's a sensor problem since sensors are more likely ignored when the engine is cold and the computer uses a default setting instead until things warm up.


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## papereater (Sep 16, 2016)

chandler48 said:


> Was '87 before injectors? If it wasn't, I'd definitely check injectors, plugs and other ignition parts They could be breaking down with added power applied.


Mine is a TBI, throttle body injector. Kinda like a mix of a carb and a FI. I have just one injector.


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## papereater (Sep 16, 2016)

Steve2444 said:


> It's been a long time since I worked on that vintage, but I'm thinking with that issue and the oil usage it may be the pcv valve.


I cleaned it, carb cleaner, and I rattled it to make sure the thing rattles, and was very loose. But who knows, once I cleaned it then bought new, and car was better, so for a cheap PCV, maybe I should buy a new one.


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## Steve2444 (Sep 28, 2020)

Just mentioning I had many years ago had a car 1974 ish that I bought used and it drank a qt of oil about every 1k miles.
I brought it back to the dealership, they replaced the pcv valve.
I ran it for years after that, never used any oil again.


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## Steve2444 (Sep 28, 2020)

papereater said:


> I cleaned it, carb cleaner, and I rattled it to make sure the thing rattles, and was very loose. But who knows, once I cleaned it then bought new, and car was better, so for a cheap PCV, maybe I should buy a new one.


Just because it rattles, doesn't mean the spring is not weak. They are cheap enough.


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## papereater (Sep 16, 2016)

FM3 said:


> If it runs great at full throttle, I'd be surprised if it's plugs, wires, air filter, etc. Sounds like a sensor problem that hasn't gotten bad enough to trip the check engine light yet.
> 
> If the car runs well at part throttle when cold, before the engine temp gets going, that's another sign it's a sensor problem since sensors are more likely ignored when the engine is cold and the computer uses a default setting instead until things warm up.


Thats what I thought. Fouled up plugs, and bad wires would not allow a car to accelerate nicely, and vigorously. It would choke/kick/spit. At any speed. Right?


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## papereater (Sep 16, 2016)

Steve2444 said:


> Just mentioning I had many years ago had a car 1974 ish that I bought used and it drank a qt of oil about every 1k miles.
> I brought it back to the dealership, they replaced the pcv valve.
> I ran it for years after that, never used any oil again.


Time to spend $4 for a new PCV valve, then I will get back to yous here. Thanks.


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## Brainbucket (Mar 30, 2015)

The one wire O2 sensor runs the show. It screws up, engine doesn't run correctly. If you're burning a quart of oil every 1000 miles, it may be contaminated. Hope it's the PCV valve but I would lean to valve seals. Using oil at acceleration. Using oil at deceleration, rings. You can test this on your driveway. Rev it up as someone looks at tail pipe. Smoke on acceleration or smoke on deceleration.


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## 660catman (Aug 25, 2019)

Sounds like the TPS or throttle position sensor. 


Retired guy from Southern Manitoba, Canada.


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## papereater (Sep 16, 2016)

Last time my O2 sensor acted up it triggered the code. So far, no codes. So, I ordered the expensive $1.89 PCV valve. Will arrive Sunday. Like Brainbucket said, hope thats it. Meanwhile, now I cant even drive the car as the L/R signal lights BOTH quit. Starting a new thread to keep things organized............


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## SeniorSitizen (Sep 10, 2012)

Many engines crank case vacuum can be checked with a water manometer made of clear plastic tubing from Ace Hardware or those bigger stores .


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## papereater (Sep 16, 2016)

SeniorSitizen said:


> Many engines crank case vacuum can be checked with a water manometer made of clear plastic tubing from Ace Hardware or those bigger stores .


 Whats manometer? I have used the narrow tube in the ear method, as that has worked for me better than the other methods, but I still cant locate a vac leak.

Meanwhile- UPDATE- Installed a new PCV and still the car runs rough, as before. Onto the next cause for the trouble. I can throw some $$ onto a new O2 sensor, I guess.


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## Steve2444 (Sep 28, 2020)

papereater said:


> Whats manometer? I have used the narrow tube in the ear method, as that has worked for me better than the other methods, but I still cant locate a vac leak.
> 
> Meanwhile- UPDATE- Installed a new PCV and still the car runs rough, as before. Onto the next cause for the trouble. I can throw some $$ onto a new O2 sensor, I guess.


The pcv may also cause the excessive oil consumption as well.

I used to have a vacuum gauge for checking for leaks, simple device.


https://www.oreillyauto.com/detail/c/s-g-tool/tools---equipment/diagnostic-tools/vacuum-testers/0a5b30b9a3a3/s-g-tool-tester/sg00/33700?pos=4


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## papereater (Sep 16, 2016)

Steve2444 said:


> The pcv may also cause the excessive oil consumption as well.
> 
> I used to have a vacuum gauge for checking for leaks, simple device.
> 
> ...


Yes, I do have a vac guage. Used it in the past, but there is much voodoo and subjective interpretation with these devices. Some diagnoses actually differ on readings/interpretations. I have found it to be a not very useful/reliable tool.


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## papereater (Sep 16, 2016)

Wow, after 3 months chasing ghosts, I should have listened sooner to the fellow members here, and checked my plugs first off! All fouled up, caked with ash, no wonder! Car now runs great!


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## SeniorSitizen (Sep 10, 2012)

Steve2444 said:


> Not sure, GM around that time installed carbs and as an option had carbs with a fuel injection feed over the barrels.
> I forget what that pos was called.


Those were the only car i ever drove that didn't need something corrected with a carburetor .


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## raylo32 (Nov 25, 2006)

IIRC, not really carbs, just a cheaper fuel injection system. Instead of placing an injector at each intake port they placed a couple of injectors in the throttle body. This was called TBI for throttle body injection.



SeniorSitizen said:


> Those were the only car i ever drove that didn't need something corrected with a carburetor .


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## Matt1963 (5 mo ago)

papereater said:


> Wow, after 3 months chasing ghosts, I should have listened sooner to the fellow members here, and checked my plugs first off! All fouled up, caked with ash, no wonder! Car now runs great!
> View attachment 726702


Now if this is a fuel injected car now you need to know why it's been running this way.....hopefully because the gap was way out of spec and not something else.

Approximately how many miles on the plugs?


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## papereater (Sep 16, 2016)

Matt1963 said:


> Now if this is a fuel injected car now you need to know why it's been running this way.....hopefully because the gap was way out of spec and not something else.
> 
> Approximately how many miles on the plugs?


Well, it's not really a FI car, but as mentioned above, a TBI. Anyway, mileage on those plugs was about 30,000, but I burn some oil, and that makes it worse. They were gapped when installed, I always check gap. But, they must have narrowed with heat/time, etc. 

I learned my lesson, people. Bottom line- the old 87 Sunbird still is running!!! Now has 229,000 miles. Too cheap to maintain, so cant junk it, right??


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## chandler48 (Jun 5, 2017)

It ain't broke. I'm at 562,000 miles on my truck and it still runs perfectly. When it completely dies, just push it off the Train Station.


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## Matt1963 (5 mo ago)

Aaa the sunbird with the turn signal issue. 

A tbi is a fuel injection system. It has an ecm and that system controls the fuel mixture so it a fuel injected car.

With those kind of miles on the car than yes your plugs will look like that so you will need to keep changing them frequently.


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