my 93 SHO is acting up. on cold start, it idles roughly. and when its cold it runs very rough, bogging down and losing power. when it gets to operating temperature it runs ok, but still seems like there should be more pull to it. i just bought this car 3 days ago and is my only major concern with this car. the guy i bought it from put an 80mm MAF. and also unclipped to o2 sensor underneath the car and put i diode in to "full" the computer. does this have anything to do with the way the cars runs???
93 SHO running roughly. any idea?
- Thread starter Keganking
- Start date
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So, umm, you are the recipient of someone else's patchwork experiment? Lucky you! Would be great IF the changes you mentioned are the ONLY changes for SURE.
That aside, an 80mm MAF is useless unless it has tuning to go with it, e.g., an LPM mounted onto the stock PCM. That could be your first problem. You should get a stock MAF with a known, good MAF sensor to swap out and test. Poor A/F info input on the intake side.
Second, why was the O2 sensor bypassed? Trying to pass a smog test/getting rid of the check light ... ??? So the engine is getting none of the feedback it is supposed to on the output side.
It is likely that you have had poor A/F ratios for a while, that have gunked up the engine/plugs/cats, etc.
Check the cats to make sure they are not clogged, or glowing hot during operation. That can quickly **** your engine.
Check the plugs to see if they are fouled, and replace as needed.
I am sure there are many other issues/questions folks will chime in with
That aside, an 80mm MAF is useless unless it has tuning to go with it, e.g., an LPM mounted onto the stock PCM. That could be your first problem. You should get a stock MAF with a known, good MAF sensor to swap out and test. Poor A/F info input on the intake side.
Second, why was the O2 sensor bypassed? Trying to pass a smog test/getting rid of the check light ... ??? So the engine is getting none of the feedback it is supposed to on the output side.
It is likely that you have had poor A/F ratios for a while, that have gunked up the engine/plugs/cats, etc.
Check the cats to make sure they are not clogged, or glowing hot during operation. That can quickly **** your engine.
Check the plugs to see if they are fouled, and replace as needed.
I am sure there are many other issues/questions folks will chime in with
integrity6987
SHO Member
I agree - get everything back in nearly stock form, else diagnosis is guesswork.
I hope you got a good deal on the car and have some money left to get it running properly. Try to find a service manual on ebay. I have one - but is useless unless the car is in mostly stock form.
As a former 93 ATX owner and grandfather of a another 93 MTX (son's car) These cars are awesome, perform well and get great gas mileage.
Best Wishes
I hope you got a good deal on the car and have some money left to get it running properly. Try to find a service manual on ebay. I have one - but is useless unless the car is in mostly stock form.
As a former 93 ATX owner and grandfather of a another 93 MTX (son's car) These cars are awesome, perform well and get great gas mileage.
Best Wishes
Ok. I will check these things out tomorrow and let you know. The guy got it on trade with another car. said he got it from an SHO enthusiast.. said he had many other cars. who knows. maybe i might find my car on this forum somewhere. thanks for all the suggestions! ill look at the PCM. it may be tuned? car runs strong.. just rough at start. and secondaries kick in.
Do you have an MTX or an ATX? How many miles on it? The thing is, the more of the history you know about the car, the better you can maintain it, right? Especially true with the SHO.
For instance, if you have a well-running full-stock SHO, it will idle smooth as silk. Power comes on earlier in the ATX than the MTX, but the MTX can be revved happily to redline. All relatively quietly.
Now put some high-lift cams in, get the heads ported, new MAF, high flow cats, mufflers, and a tune to go with it. Won't be the same car you started out with. You may have a lopey idle, you may have to step on the gas a bit to keep it running at stop lights, and lose traction in first gear, but it will pull like nobody's business. Add in a supercharger or turbo setup, and lookout!
Hopefully the car was maintained properly. If you can post some goodsized pics of the engine bay/exhaust/etc. many people will be able to tell accurately what you might be dealing with.
For instance, if you have a well-running full-stock SHO, it will idle smooth as silk. Power comes on earlier in the ATX than the MTX, but the MTX can be revved happily to redline. All relatively quietly.
Now put some high-lift cams in, get the heads ported, new MAF, high flow cats, mufflers, and a tune to go with it. Won't be the same car you started out with. You may have a lopey idle, you may have to step on the gas a bit to keep it running at stop lights, and lose traction in first gear, but it will pull like nobody's business. Add in a supercharger or turbo setup, and lookout!
Hopefully the car was maintained properly. If you can post some goodsized pics of the engine bay/exhaust/etc. many people will be able to tell accurately what you might be dealing with.
its a 93. MTX. 138,000 on the body, and under 100,000 on the motor. motor, tranny, interior and wheels are from a totaled car. the motor has been apart. the valve covers are painted a nice red. my cats do not glow red. i need to get a stock MAF and take out the diode and plug the o2 back in and check the codes. will post pics soon. damn hood release broke, so i have to find a way to open my hood and rig something....
BlooDSMeaR
New Member
Good luck? I am currently working on a 93 SHO that was worked on by knuckle dragging GORILLAS. Every part has be torqued way past the legal limit. Wires are chopped and spliced. I am having a nightmare of times with it. I can feel your pain.
Once you get it sorted out and it still runs on 4 cylinders check your codes... wait did you already do that? Whats the numbers. We can help you out a lot more with all the information.
Once you get it sorted out and it still runs on 4 cylinders check your codes... wait did you already do that? Whats the numbers. We can help you out a lot more with all the information.
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