So we just picked up an 85 4+3 Z51 Car. Its got a fresh ZZ4 Motor and other than that it is what it is and nobody has any information. Its got the original TPI Injection on top and Long Tube Headers leading into a stockish Exhaust. The seller warned Us not to drive it far its got "issues" . So it would Start and Run pretty good as is so we headed for the Highway chase Truck close behind. Low RPM OK but 1/3rd Throdle it would fall on its face and ping. Made it 50 miles or more to our Exit but was loosing power all the way and then died. Once Dead it was real Dead turn the Key and not even a click. Ok so charging not working so when the Battery died that was it right. No Headlights and Radio Fine. Called for Tow and when it showed up it started right up and drove it on the Truck all tho backfireing back threw the TPI. Now thats all it wants to do we have Tried moveing the Distributor looking for a sweet spot. Looking around its got a bunch of new sensors somebody before Us has been throwing Parts at it. My Guess is to try a new ECM. The Wireing is a bit to be desired it looks like somebody was in a hurry to get the L98 out. We have an apointment with Blood Ent. in Auburn Wa 10 days away and I'm sure they will figure it out. We are going to clean it up and go threw all the easy stuff plugs and caps and Wires etc. Anybody got some good Idea's on whats going on.???

 

Sounds like you may have low fuel pressure. There is a port on fuel rail, buy/rent/borrow a gauge and tape it to the windshield so you can monitor fuel pressure under load. Should see around 32 lbs at idle and a few more under load.
You may also have a poor connection at battery terminal, causing the no start>start situation.

 

Also, check for any stored codes in ECM.

http://www.corvettephotographs.com/c4vettes/ecm.htm

http://members.shaw.ca/corvette86/No...it%20Check.pdf

 

So far we havn't seen a Check Engine Light but I'm not sure if we have any action in the Panel at all. Planning on going in there and see if anything like Bulbs are missing. Since the Engine has recently been replaced we are going to check to see if the Grounds are all hooked up. I have a Code reader and I also have Gordons test plugs. A new Fuel Filter is planed tonight along with some underside cleaning. I have fuel Pressure gauges to use as well.

 

The factory Cat has the Tube leading out of it and its Cracked off near the Oil Pan. Somebody has done some interesting Welding and Hose Clamping on it. So when one eliminates or replaces the Cats what is done withthis line? I guess I'm not sure what it dose. The only cats I have delt with didn't have it.
Were is the ECM on a 85'? It sure isn't were my 96' GS is. I see e-bay is full of them and Camaro's and such use the same one. I'd prefere to get a complete Corvette one and not change anything over.

 

Make sure you unplug the EST wire and use a timing light to set the timing at 6-deg BDTC. The computer controls timing from there. Every timing setting will be off -- if you change the distributor's physical location. Search my userid and you will find a thread (with pics) on this topic. It was last fall.

I'd also verify the spark plugs are routed correctly.

The ECM is up under the PS dash.

The tube going to the cat is the AIR tube. It's a simple system to blow air across the CAT to accelerate the heating/incineration process. Performance builders completely eliminate this tube.

 

Did the Car leave Bowling Green with the Engine Ground Wire attached to the Lower Motor Mount and then attached to the Frame near by as per C3 and many Chevys leading up to the C4?? If so I don't have the Wire or even the Bolt. Got a little side tracked last night the Parking Brake didn't work to well and found that the LH had had the Shoes and all the other Parts removed! Pressure Washing tonight plan on working on a cleaner car tomorrow.

 

No the ground goes to a bolt above oil filter, along with a strap that goes to body and about 6 from ECM.

 

Did you performe the fuel pressure test mentioned and set your timming yet? A manual is a must in these situations, good luck! Let is know the timming and fuel pressure results.

 

Sounds like a bad MAF to me. Disconnect it and see if it goes away when running on backup. If so, it needs a new one. Seriously doubt plugs or any typical tuneup parts are going to do anything. A backfire through the intake can be caused by an air pump that doesn't vent overboard during decel, but your mods lead me to believe that it's been deleted. If it is still there - and it isn't a bad MAF - clamp off the hoses to the headers and see what happens.

 

Thanx....Thats just what I needed. The Main Cable is hooked up but the Strap was hanging loose and we didn't know where it went. Thanx again.

 

OK so I have an update we had the Car in Blood Enterprises Auburn Wa. yesterday. Prior to takeing the Car there we found the following.

Ground Wire mentioned above, Check Engine Light missing, Ohm'd out Fuzes OK but replaced anyway due to corosion, Found a Burned Plug Wire and replaced set, replaced Battery, Presure washed and just straighted a lot out.

At Blood Ent. We found;
Bad Fuel Pump Solinoid, bad Starter Motor Solinoid, Bad Ox Sensor, Broken Ground Wires behind Distributor, ECM Prom was still original and reflashed a new one that now has ZZ4 perameters, Replaced ECM with a Reman,Timed Distibutor. Ajusted Fuel Pressure.

So now we have a Car that runs and drives, well almost I have a Mini Starter on order, we were knocking to Solinoid all day yesterday to get it to Start and it gave up last night. The ZZ4 is strong and dosn't sound like it has any issues I think it will give my 96 LT4 a race.

So overall we bought somebody elses project gone bad. They spent the time and money to replace the Engine and Componets but never took the time and money to take it to a Tuner to make it run right and be able to enjoy and drive it.

I'm replacing the Starter with a Mini Starter to get some clearance away from the Headers the Car has now. I have the GMPP one headed our way from Summit. I used this one 25 Years ago on my 80' and its still running fine however this one dosn't look the same. The Ox Sensor needs to be replaced with a heated one due the Headers Cooling effect.

Next will be to take the Car to an Alignment Shop to see how Straight this Car is and find out if its a Keeper for the Autocross Tracks.

I don't think we are done with Wireing Issues, wich are known trouble spots on early C4's if we had the Engine out it would be nice to just replace the Harness. The Cat is blown out and not in very good shape and I will probably be replaceing the Exhaust from the Headers back to the Mufflers. Since one Header needs to be removed to get the current Starter off this may happen sooner than later.