Anyone want to tackle this?

[adfac]

Hi. I'm a newbie and have owned an 86 vert since October 07. I bought it from a guy who blew the engine by driving it after the oil pressure dropped to 0. I got a good deal and within a week had a mechanic drop a new L98 engine in it. The car runs just fine, except for the "service engine soon" light which comes on almost at startup. I've done everything I know how to do. I bought an FSM and a code scanner (AutoXray 2000) and learned to pull codes. My mechanic stays very busy and I'm not sure I have his attention as the last couple of times out there, he's tried to figure this out but with no luck. It's like he's given up on it. Anyway, he got a (Idle Air Control) code (I think it was a 15) on his scanner and said the IAC connector was bad. It was a little beat up, so I ordered a new one and he put it on this morning. Nothing changed. The Service Engine Soon light still comes on at startup and stays on until you shut the engine off. It is not an intermittent problem. My code scanner (the AutoXray) reads a 42 (Electronic Spark Timing Monitor Error), a 41 (Electronic Spark Timing Error), a 34 (MAF/MAP Sensor too low), a 32 (EGR Failure) and a 25 (MAT is too high). Yep, it throws 5 codes in one read! But the car is running fine! New engine, New ECM, MAF has been thoroughly cleaned and everything under the hood including the injectors is in good shape. I just don't know where to start. I don't have a test probe or voltmeter and don't know how to read them anyway so I was wondering if anyone has had a similar problem with the "service engine soon" light coming on while the engine runs fine. Thanks for any advice. :confused

 

[Happydad]

I would start with checking every stinking connection on the engine ...Making sure nothing is cut ,no wire insulation showing bare wire,fully seated connectors and most important that they go to the proper sensors..One reversed sensor could throw a multitude of codes..Even a missing wire will throw multiple codes..Since you didn't install this engine checking thoroughly would be wise..If that is cool(the routing and connections that is) according to the FSM,Then start tracing the lowest code first...A meter will help and is almost a must,So buy one,borrow one..Buy a 12 pack and invite a friend over that knows how to use one...And get cracking and keep us posted

 

[Ezmunie]

Sounds like Happydad has a pretty good starting place I am sure others will chime in and offer more advice and help, so be patient In the mean time, welcome to the

 

[gmjunkie]

I would start with checking every stinking connection on the engine ...Making sure nothing is cut ,no wire insulation showing bare wire,fully seated connectors and most important that they go to the proper sensors..One reversed sensor could throw a multitude of codes..Even a missing wire will throw multiple codes..Since you didn't install this engine checking thoroughly would be wise..If that is cool(the routing and connections that is) according to the FSM,Then start tracing the lowest code first...A meter will help and is almost a must,So buy one,borrow one..Buy a 12 pack and invite a friend over that knows how to use one...And get cracking and keep us posted

And Check and Clean every Ground!!!

 

[air1jpg]

First thing is
Did your new engine come with a warranty? It seems to me that the mechanic would be responsable in some way to get your engine running properly after he installed it.

 

[JAKE]

I had an 86 too, before it was totalled by an 18-wheeler, so I've had my share of SES codes, too.

Here's how I'd attack the problem:

I'd first disconnect the battery for about 30 seconds to clear all the stored codes. I'd then re-connect the battery, fire the engine and see which codes (if any) return.

Checking the ground connections - as someone already recommended - is an excellent idea. On the driver's side, lower area of the block there are a few ground wires. There's also one that runs to the chassis in the same area; if memory serves it's a braided ground strap. It should also be connected. Any grease, oil, etc., or loose connection could be causing an intermittent ground condition.

A scanner that shows, in real-time, the activity of the sensors would be an excellent way to track down a sensor(s) that's not operating within it's designed range.

A digital volt/ohm meter (there are a lot of inexpensive ones out there) will allow you test the connectors. An inexpensive 12 volt test light will be needed too for some tests. The FSM has very detailed step-by-step procedures on how to test the various connectors to see if they are receiving the correct voltage or resistance.

Remember, a single problem could cause multiple codes to be set. Cure the single problem and several, if not all, codes may disappear. Basically it's just a matter of putting aside an afternoon/day to track down the cause(s).

Time and patience.

Hope this helps.

Jake

 

[geekinavette]

Yep this sounds like the classic case of "oops forgot to attach that ground wire". I have no idea where they all are on the '86, but on the '84 there's one on the back of the driver's side cylinder head, and on the same side of the transmission bell housing. both of these provide a return current path for various sensors and are very often missed when installing an engine and/or transmission.

Bill

 

[JAKE]

If I remember correctly, there's a ground wire that connects to the back-side of the driver's side head too.

When I swapped to aluminum heads on my 86 I didn't trust aluminum to provide enough of a ground, so I connected that particular wire to a cast iron location. I forgot where I actually made the connection, but it was right in the same general area; probably the block.

Be sure that all ground locations, ground wires and bolts are free of grease/oil/rust/etc.

Jake

 

[geekinavette]

Not really thread related...but for future reference there's no need to worry about aluminum in that respect...it is a very good electrical conductor.

Bill

 

[JAKE]

Not really thread related...but for future reference there's no need to worry about aluminum in that respect...it is a very good electrical conductor.

Bill

Thanks for that, Bill. Since I didn't know aluminum was as good a ground material as cast-iron, I just decided to use the same material as GM did for the ground.

Jake