Help: 1988 4.5L extreme rich fuel

[bdiamond]

1988 Cadillac Sedan DeVille, 4.5L V8, 143K on the odo.

Background: bought the car and rebuilt the upper half of the engine after it

overheated and warped the heads (previous owner). Bottom half was in excellent

condition, after 14 years of Mobil 1 changes and regular servicing.

Turned the key and it started immediately, idled and ran perfect, very smooth

and powerful. I drove it around town for 2 week and took a couple of 50 mile

round trips. Everything seemed prefect. I was really happy with it.

Then 2 days ago, in a instant it started to run really bad, through out the rpm

range. It also exhibited a hard down shift to low when pulling up to a stop. It

does not backfire through the TBI or the exhaust. Also, it has a hard down shift to 1st on pulling up to a stop. And the brakes are poor due to low vacuum.

I rechecked all plumbing: all good. Wiring: all good. No visible signs of any

abnormalities.

I pulled a couple of plugs: very fouled with black, damp, sooty unburned fuel.

I deemed that I should have rebuilt the TBI while I had the engine apart. So, I

installed a TBI overhaul kit: the fuel pressure regulator diaphragm looked

worn, but not worn out; and the other seals also looked ok. I reinstalled the

TBI and started it up: same problem. I noted the injectors were spraying what I

believed to be a LOT of fuel at idle.

Next I tested the ignition system thinking the a poor spark could be the

problem: resistance checked the coil: ok; resistance and ground checked the

pickup coil: ok. However, the button in the top center of the distributor cap

that has a little spring the presses into the center of the coil was

incorrectly installed in the past. it made very little contact with the coil.

Black crud had developed on the contact area on the coil. I corrected this and

reinstalled the coil and the distributor on the motor. Started it up: same

problem.

I vacumm tested the brake booster: ok.

Gentlemen, what am I overlooking here?

Any help would be greatly appreciated.

TIA

Bill

[bdiamond]

I will try the injector disconntect tomorrow.

Yes, the only trouble code that appeared in the last few weeks since rebuild was E30.

[bdiamond]

Yes, the injector on the left bank side bleeds fuel (a lot) until the fuel pump shut off. then it slows reduces and stops (about 5-10 seconds). Righ bank injector stays dry. Thanks for the tip.

[bdiamond]

bbobynski,

I picked up a used TBI unit from a junk yard.

The used injector is labled:

GM5235132*RPD

1295 GM

The ones in my 1988 caddy are:

GM5235203*RPD

2058 GM

Do you know if the used injector will work?

TIA

[millwright71]

Don't know if the used one will work or not. I believe these injectors are pretty reasonable in price at auto stores like Auto-Zone or Advance. Maybe you can have them cross reference the number on the used one you just bought.

[bdiamond]

Crap, it wasn't the injector after all. When I installed the tbi kit, I clipped the lower "O" ring on one of the injectors and that was causing the fuel flood. Corrected that. Now I have strong spark and fuel and it just won't start. it putters. It sure sounds like the timing chain jumped.

Anyone ever hear of these 4.5L V8's jumping the timing chain? Can valve timing be checked with removing the timing cover (ugh)?

TIA

[bdiamond]

I just check the timing as per instructions. It was a fraction off: 6° BTDC; moved it to 10°. Start car: same problem.

After the car sat overnight, it did start this morning,: same chuga-chuga tune.

Really, it sounds as if there is water or another contaminant in the fuel. I pump off about a pint of fuel from the fuel pressure test port: can’t see any water in fuel. I am going to pump off about .5 gal and drain my lawn mower and test the fuel.

Also, I did the following test: manually cranked the engine at the crankshaft while an assistant carefully watched the distributor rotor for movement. Then slowly backup the crank to the point where the rotor began to move. Did several times to verify. There is 5° of slop.

Do you think it would be worthwhile to video the running engine and then make it available for streaming over the Internet so you can hear/see the running behavior?

[bdiamond]

PS: I checked the distributor gears: good, no abnormal wear.

[bdiamond]

update: fuel tested ok.

Problem still exists.

[KevinW]

After the car sat overnight, it did start this morning,: same chuga-chuga tune.

Sounds like sitting overnight helped to clear a flood condition. Are the plugs still covered in carbon? It's possible an ECM driver problem is affecting one injector. How does the spray look under a strobe light?

[bdiamond]

the injector pattern looks like a cone.

latest update: I swapped the injectors with 2 units from a junk car (85or86 Caddy with 4.5L RWD). I cound not verify if the injectors are calibrated the same as the originals (original: 5235203; used: 5235132). result: engine still chuga-chugs, too rich.

tested so far:

TPS: good

ICS motor: good, (but will set E30 as per TSB 88/10/03 T89-24)

MAP: good

Basic timing: 10 BTDC

Vacuum leaks: can't find any

Plug wiring: checked with inductive timing light, all plugs are firing

Plugs: new two weeks before problem developed, platinum. Now black with soot/carbon.

Oil: good, no water or obvious contanimation

IAT: oh no, its bad. It reads from 1.6 ohms (cold) to .44 ohms (hot). I will check again tomorrow to make sure this is right.

Would it make sense that the ECM would run the injectors super rich if the IAT is out of wack?

[bdiamond]

My digital meter had a low battery yesterday. The IAT is actually reading about 10% low.

[KevinW]

If the injectors came from an '85 RWD model, they're for an HT4100. The '86 RWD had a carbureted Olds V8.

The inductive timing light shows there's some current in the ignition wires, but it doesn't mean a spark is occurring in the combustion chamber. The ignition energy will find the easiest path to ground, which could be the carbon coating on the insulator. You should clean the plugs thoroughly or install a new set.

Did you test the MAP by direct measurements or did you monitor the ECM data via the OBD?

If all the inputs are correct, the fault may be in the ECM hardware. A used one should be inexpensive; remember to transfer the Memcal/Calpak.

[bdiamond]

Carp, carp, carp. Did a compression test today. 180 psi in every cylinder, except the last one tested, #8, dead zero. I tested it 5 times. Zero compression, not even 1 psi. I squirted oil in the spark plug hole: still zero.

PS: no coolant found in the oil and no oil in the coolant.

Looks like another teardown. I hope City Motor Supply (Dallas) will stand by their cylinder head (assuming it is the head or valves).

Thanks a lot to everyone who tried to help.

Bill

[bdiamond]

chuga-chuga problem finally found. The intake valve spring in number 8 cylinder failed. Also, the bridge piece that goes from the intake rocker to the exhaust rocker in number 4 cylinder snapped in the middle and a chunk of the bar about 1/4" long was laying in the oil.

thanks all for the help.

[bdiamond]

Final post to this thread:

The 4.5L is running perfect now, well almost.

The intake vavle spring in #8 cylinder had broke into 3 pieces, leaving the valve hung open. This caused very low manifold vacuum, which caused the MAP to signal WOT to the ECM which sent very rich fuel fuel pulse wifth to the TBI (my reasoning). A new spring (from the head reman people, no warr. on the labor) fixed the problem. 180 psi in all cylinders now.

All that without any codes. A compression test found the problem. My bad, I didn't think to do a compression test because the heads were new and the car ran good for the first 200 miles.

Thanks for the tech help, Caddy group people.

Bill

[anton 60 caddy]

Hi there.I had the same problem on my 88coupe,i know this might sound daftbut it fixed it and she runs spot on know.Change the tempreture sender unit on the intake manifold,cost me £20 here in the UK. Before i changed this it ran as rich as hell,black smoked and sounded like a concrete mixer on overtime.Hope this helps Anton.

[GoRicky]

Yes - thanks for all of the info & I can sympathize with the distressed owner... I always wanted an Allante' when they were new, but couldn't afford one.  I 'brilliantly' picked out a (white) '91 model because of its "great, easy-to-work on" 4.5L V8 (200 HP) engine.  I bought it from the original owner w/ 23K mi.  I drove it from Colorado to Texas & within 24 hours, I jumped in & moved it to higher ground, because of a 50-year flood & the underside took a beating from debris.  I was told 'the oxygen sensor probably got knocked off' & 'no problem'... when my wife saw what a beautiful car it was, she said I WANT ONE, TOO!  Luckily, Barrett-Jackson sent me an email, sporting a wonderful (black) 1-owner example w/ only 34K miles, 'everything works' & truespoke wheels; I told B-J I couldn't wait for it to be delivered & it came w/B-J paper floor mats, a tote-bag & other goodies.  Both - (1) beautiful, (2) perfect interiors, (3) straight and undented exteriors.  The white one has a noticeably thicker ragtop, as the former owner said she shipped the car to CA "you know - to that place that makes/replaces Rolls-Royce ragtops".

Happy, Happy, Happy!!: Only thing is -  neither one has run right.  Not only that, they were NOT perfect with respect to stereo systems, lighted mirrors, batteries, doors hung right, tires, etc... I commenced to having everything fixed (I am not a 'modern' mechanic).  I took both to a family-owned mechanic shop I've done business with for 20+ years & told them to do 'complete tuneups' i.e. new filters, hoses, plugs, wires, coolant, lubes, batteries, oil, tires, etc. & gave them the SHOP MANUAL I bought on ebay.  Well - pick one up, drive it 2-3 mi. & then engine runs REAL rough & the tranny shifts real hard.  At idle, the cars just shake & ca-chug-ca-chug.  After taking them back for a THIRD time, I gave up & chugged down the street to another shop that works on everything from tour buses to motorcycles.  I now have over $3K invested in each & wouldn't drive either to buy a loaf of bread.  They both do the same thing... crank up - YAY!  Drive 2-3 mi. & they start missing to the point of even dying in traffic.

They still look great & are almost cosmetically perfect , but NEITHER ONE will run for more than 4 minutes before - strangling on fuel? losing the timing setting? I've paid for injectors to be ultrasonically-cleaned & several injectors to be replaced.  The last time I put the white one in, I had to have it TOWED.  Is there someone in this whole world that is an expert on the 4.5L engines?  Should I take it to the Caddy dealer?  I am REAL disappointed in these two independent shops.  They don't burn any oil & the motors look perfect.  HELP! - Thank You!

[BodybyFisher]

It sounds like once the engine is up to operating temp and goes into closed loop the problems begin.

This is TBI or throttle body injection correct?  I just worked on an 89 chevy 5.7 with TBI and converted it to a Holley carburetor for the owner.  But everyone I spoke to said the TBI is a good system.  TBI is the first generation of computer controlled ignition.

You need to find a mechanic who either understands TBI or who will invest the time to learn it.  Look for old timers, I don't think it will be easy to find a mechanic who understands the system even at the dealer, it is 31 years later.

It is terrific that you have the service manuals.  We have a member that may be helpful I will page him he may be of some help @OldCadTech

@GoRicky

 

[OldCadTech]

Do a OBD code check first...

Black smoke from exhaust?

Sounds like too much EGR maybe.

@BodybyFisher

[BodybyFisher]

19 minutes ago, OldCadTech said:

Do a OBD code check first...

Black smoke from exhaust?

Sounds like too much EGR maybe.

@BodybyFisher

Thanks John, I have been thinking of you lately, hope all is good.  Ill call soon.  @OldCadTech

[GoRicky]

Thanks everyone for the input!  I'm gonna make calls to find a good TBI man.  In the old (carburetor) days, I would have said 'maybe the choke is sticking & floods the engine when it gets warm'.   I'll keep posting, so maybe somebody else won't go as crazy as I've gone!

[BodybyFisher]

3 hours ago, GoRicky said:

Thanks everyone for the input!  I'm gonna make calls to find a good TBI man.  In the old (carburetor) days, I would have said 'maybe the choke is sticking & floods the engine when it gets warm'.   I'll keep posting, so maybe somebody else won't go as crazy as I've gone!

If you have the manual, look up how to check the codes and post them here.  Ill do some digging to see if I can find the procedure.   We should be able to help you, so that you can go to a mechanic knowing what the problem is.  

Confirm that both are 91's please

@GoRicky

[BodybyFisher]

How to check codes on the 91:

1) Turn ignition ON.

2) Simultaneously press and hold the A/C control panel ‘OFF’ and ‘Warmer’ buttons

3) When all segments of the display  illuminate: Release the A/C control panel ‘OFF’ and ‘Warmer’ buttons

4) Trouble codes will be displayed in the driver information center

5) Trouble codes will be displayed in ascending order, have a pencil and write down all codes or make a video with your cell phone and write them down later. 

All ECM codes start with the letter ‘E’. Trouble codes for all systems will be displayed.  Include whether the code is current or history

All current trouble codes end with the letter ‘C’.

All history trouble codes end with the letter ‘H’.

If no ECM trouble codes are stored, ‘NO ECM CODE’ will be displayed.

When all trouble codes have been displayed, Press the ‘RESET’ button

Turn the ignition OFF.

Post your codes here and we will help.  The codes will direct us to problems.

You can look up the ECM codes here:

http://www.caddyinfo.com/stscodes.html

@GoRicky