Lumina Z34 needs help!

Howdy, I have been working on a 1994 Lumina Z34 for a friend. The car has a 3.4 liter DOHC engine. The car has been starting ok and seems to run fine until it gets up to normal temperature. Then the service engine soon light comes on and the engine hesitates severely, lacks power, and idles rough. So far I have pulled the plugs and cleaned them (looked normal), did a compression test (blew 150 across the board), and checked all connections. I have a fuel filter for it but haven't got to it yet. The owner of the car recently paid almost $400 dollars for a tune up at a GM dealership after she experienced the problems. From what I gathered under the hood,<br /> that $400 bought her a set of spark plugs and 3 new plug wires! I intend to change the fuel filter but suspect a bad EGR valve, mass airflow sensor, or oxygen sensor. The EGR is almost $200 and the 02 sensor is $60 so I want to get it right the first time! Any suggestions would be appreciated, by the way the car has about 115,000 on it.

Re: Lumina Z34 needs help!

Maxx,<br /><br />Take a run down to the local AutoZone and have them hook up the code reader to the cars computer. They can then translate what the codes refer to. Be careful as just because the computer says one thing is the problem, it may be related to another issue. Example, the oxygen sensor may flash a code as the problem, but it may be the spark plug wires causing incomplete combustion and give the appearance of an oxygen sensor failure.<br /><br />Get a reading and repost. There are some extremely skilled engine mechanics here and the more information given the better the solutions offered. <br /><br />FYI some EGR valves can be cleaned up with a little brake cleaner. Make sure you don't lose the gasket. Make sure the little plunger moves easily and reinstall.

Re: Lumina Z34 needs help!

Run a code scanner on it first... No point in throwing parts at it if ya don't know the cause...<br /><br />To troubleshoot the EGR, disconnect and cap the vacuum line from egr valve... If the performance problem stops with vacuum disconected (check engine light will still come on) then you've isolated the problem.. <br /><br />Egr may just need a good cleaning.. They get sooted up..

Re: Lumina Z34 needs help!

Like snapper said. If you are getting a service engine soon light it is putting a code on your computer which should help you isolate it. My guess is an ignition module

Re: Lumina Z34 needs help!

You can just do like my Father-in-law does, put a peice of electrical tape over the light.

Re: Lumina Z34 needs help!

Have you checked the catalyic converter? Rough running, no power, hesitates, 134k miles. Could be the converter and that can play games with the emission control sensors. Feel the exhaust with your hand, really hot air is a symptom of the converter being plugged. Benchmark the heat with another car first. If too hot, take it down to the local muffler shop and ask them to check it. All they do is open the pipe and feel the flow...experienced hands can tell if it is flowing the right cfm.

Re: Lumina Z34 needs help!

Thanks for all the advice guys! I decided to take the advice of Pointer and head to the local auto zone which is about 10 minutes away. I figured that would be about enough time to get it up to temperature which is when it usually started showing symptoms. But as my luck would have it I drove the thing for more than a half an hour and it ran like a top! After remembering that the manual said the computer stores the codes and can be accesed even with the light off I turned around and went back to give it a try.I went in to a suprisingly busy store only to be told by the kid that the warning light has to be on in order to check it. The 2 employees that were there seemed overwhelmed with customers so I figured I'd go drive it around a little more and see what happens. Went out to the lot,car wouldn't start-dead battery WHAT NEXT! I then had to go back in the store with my tail between my legs and borrow there little "starter pack".Drove it home, put it on the charger for 2 hours, then took it out again, ran perfectly. Changed the fuel filter and took it out again, no problems. Tomorrow I'll clean the EGR as suggested. I know as soon as I give the car back to the owner the problems will arise Thanks again guys, will keep you posted!

Re: Lumina Z34 needs help!

Well the news sounds crummy. Drive her until she acts up again. When the battery went dead you may have erased the codes. <br /><br />The catylitic Converter is a good suggestion. Good luck and keep posting.

Re: Lumina Z34 needs help!

pointer, it sounds like an oxygen sensor, when cold it doesn't do much but when it warms up it will give you problems. P.S a paper clip works great to pull codes, get a haynes manual there basic and shows the codes for the OBD1 system