1989 5.0 problems after plug wire change

Sn8kebitten

Well-Known Member
Established Member
Joined
Sep 18, 2011
Messages
2,004
Location
Kentucky
Trying to help a friend that just bought a '89 LX 5.0. The car is a stock auto besides BBK shorty headers.

The car ran and drove fine when he bought it two weeks ago, but at WOT, the check engine light would come on above 3500rpms, then would go back off as soon as you let off the throttle. Otherwise would run and idle fine.

So he changed spark plugs and wires with Autolites and Napa premium wires to see if that would help the WOT issue as the plugs were pretty dirty. Well after that, the car wouldn't even turn over. With three known good batteries. The negative terminal started smoking so we stopped trying to turn it over and he eventually replaced the starter solenoid and the positive and negative wires all the way from the block/frame to the battery.

After the new battery wires, the engine will fire now, but only if you hold the throttle halfway down and even then it runs like crap and will die as soon as you let off the throttle.

He triple checked and then I triple checked that he ran all the plug wires correctly. But another thing he did was spray throttle body cleaner into the throttle body because it had a lot of crud built up around the blade, and then he cleaned the MAF with MAF sensor cleaner making sure to put everything back how it was.

Do you guys have any idea what the issue could be? Trying to think of more info to add but I'm typing this at work
 

railroad

Well-Known Member
Established Member
Joined
Dec 9, 2003
Messages
2,118
Location
warrior, al
Pull the plugs and spin the engine over. Sounds like he got too generous with the TB cleaner and hydro locked the engine.
On the check engine light, get the code read and have someone else fix it. I am restraining myself from commenting on stuff people do to f up a car.
 

PaxtonShelby

iamdrab
Established Member
Joined
Nov 16, 2010
Messages
5,434
Location
Pittsburgh, PA
You would need to use one heck of a lot of cleaner to hydro-lock the engine.

Running very rough could be due to knocking off an a vacuum line.

Are you sure the replacement plugs are the correct part number...and gapped correctly?

Were the cap and rotor replaced as well?

Dielectric grease in the plug boots? Some aftermarket wires are junk.
 

Sn8kebitten

Well-Known Member
Established Member
Joined
Sep 18, 2011
Messages
2,004
Location
Kentucky
Wouldn't it only be considered hydrolocked if it didn't run at all? It runs but only with throttle at 50%. And also, isn't TB cleaner flammable/combustible anyway? Not sure how using a throttle body cleaner for maintenance is considered ****ing it up.

They were gapped at .048 as per a guide he read but I later found one saying 87-93s should be gapped at .044. Not sure that small of a difference would matter though. Cap hasn't been changed yet but I told him that's what he should do next. I may try to go put the old plug wires back on it and see if that helps
 

railroad

Well-Known Member
Established Member
Joined
Dec 9, 2003
Messages
2,118
Location
warrior, al
The engine not turning over was probably the result of the hydro lock. A cylinder does not have to be full to lock the engine. The piston cannot compress a liquid.
One half an inch, one quarter, one eighth, etc in a cylinder can stop the piston from reaching TDC, when this happens, all rotation is stopped. Fortunately TB cleaner evaps very fast and is thin. Between evap and leaking past the rings, it will dissipate.
On the half throttle issue, it could be a puddle in the intake. Adding oil residue to the cleaner will slow the evaporation and it might stay there until the engine goes through a good warm up.
,,,can only guess on his work.
good luck,
 

Sn8kebitten

Well-Known Member
Established Member
Joined
Sep 18, 2011
Messages
2,004
Location
Kentucky
So I've been out of the 5.0 game for several years now. Was looking at the wiring diagrams he showed me that he was using and I decided to pull them up myself on my phone. That's when I remembered these 5.0 HO's have a different firing order from older 302 engines. Found an HO diagram that was completely different from how he routed the wires and I swapped them around real fast.

Runs like a dream now lol no more check engine light at WOT either. Now he can finally get the car out of my driveway. Thanks for the help guys
 

Users who are viewing this thread



Top