Stephenms

I'm just curious as to what you guys think my issue could be!

I have been diagnosing my 1987 for about a month and a half now. It's misfiring, stumbling when I accelerate and will slip when trying to downshift after I punch the accelerator, rough idle and just all out a frutrated car, lol.

I ran codes with a live feed scanner and it said my open loop was reading at 20 points. These cars like 128. Anything above and below is the lean/rich mixture being read by the computer. The computer is reading way LEAN. However, I had a few codes that popped up. Mass Air Flow Malfunction (a new MAF did not fix my issue), Knock Sensor Malfunction (I rewired it so it was much further from the spark plug wires, did not fix my issue), TPS malfunction (I have had NO time to fiddle with this one), Burn Off Relay (swapped relays and no change, I did purchase two new relays for MAF power and burn off)

I replaced the old MAF with a new non-original design MAF by Rich Porter, they have amazing reviews since the original design was crap. I replaced the O2 sensor with a Denso OE and no fix. I followed the wires from the MAF and TPS and they checked out okay. I followed and cleaned the IAC and wires.

My cats get hot enough to steam the water that sits in my insulation so i am not driving the Vette. My catalytic converters are bad due to the car sitting 2 inches from the ground so they get dinged up from speed bumps. Exhaust smoke escapes from them on both sides which only used to happen when I was running city at 220 degrees, now it does it at 180 degrees. I am not sure what my issue is.

Before this all happened I did a 9th injector delete so it sat for a week before it was all done and now it's having all these issues. Could I have a bad ECM? Could my cats be clogged so bad causing the O2 to read incorrectly? I can get a rebuild ACDelco ECM for about 90 bucks shipped.

Any ideas?

Stephen

DUB

Is the car going into 'CLOSED LOOP'?????

The TPS code is NO JOKE....find its problem and fix it.

When the scanner had 'LEAN'...is your scanner saying that is LEAN OXYGEN...which means RICH FUEL....OR....LEAN FUEL ...which means rich oxygen.

That ''reading 20 points''...is that your integrator value??????

Is your coolant temp sensor that is sending info to your scanner reading a correct value?????

You need a 'back pressure gauge' to see if your pre-cats are bad or not. Having exhaust leaking from them IS NOT GOOD.

Have you verified fuel pressure????

DUB

Stephenms

Sorry for the late response! I've been busy with work.

I haven't had much time to work on the beast.

I WILL check and replace the TPS.

I was told my issue could be fuel flow is lacking or my cats are clogged.

My memory is fuzzy on the readings from the scanner. The value of the O2 sensor was very low, at a solid .20 value. Being an OBD1 car I did not have much live feed options.

So this far I've trialed out the MAF sensor, O2 sensor, IAC, vacuum, wires, plugs.

DanielRicany

Usually if the TPS is malfunctioning, a MAF code may set as well. And since acceleration enrichment works off of TPS, that's probably why you are running lean which is setting off the knock sensor.

Anyway. If you put a voltmeter to the blue wire of the TPS, and the other probe of the voltmeter to ground? What is your reading? On the other two wires of the TPS you should have 5 volts and ground.

You really need a graphing meter to accurately see what's going on during the following test. Maybe you can borrow one.

Place one probe from the graphing or voltmeter to the signal terminal of the sensor and the other probe to the ground terminal of the sensor. The sensor must be disconnected to do this. Then slowly move the TPS back and forth all the way and look for any dead spots. On a graphing meter it should show up as 0 volts. Same thing on a voltmeter but they are a lot slower at reporting data than graphing meters. Move it back and forth about 20 times. If you find a dead spot, get a new one.

Report back with your results.

ToniJ1960

Might be a situation where a good old voltmeter would work well?

Stephenms

After lots of testing and fiddling with this thing, a dead spot was found. I know I purchased one of these suckers a month or two ago wanting to reset all my idle readings including idle screw and all but now I can't find the sensor. I'll have to look a little harder or I'm buying a new TPS.

As for the cats, I get discounts at work for exhaust parts including piping, I'm thinking of getting a set of 18inch pipe so I can remove both cats and clamp new pipe on, I think this will eliminate my slight exhaust manifold glow and smoke bellowing into the engine compartment and from underneath the vehicle. I'll keep you posted.

I appreciate all the help. I'm finally getting some vacay days, hopefully soon I'll have my baby back on the road again.

Tom454

Same symptoms on my 87 with 104,000 miles. Removed the distributor cap and rotated the engine back and forth via the crank/damper bolt. The distributor rotor barely moved with more than 20 degree's crank rotation. Will be installing new timing chain & gears.

tunedport85inject

minimum and maximum BLM allowable are 108-160, 128 means no PW correction for target AFR.

[QUOTE]My cats get hot enough to steam the water that sits in my insulation so i am not driving the Vette. My catalytic converters are bad due to the car sitting 2 inches from the ground so they get dinged up from speed bumps. Exhaust smoke escapes from them on both sides [QUOTE]

Gloving exhaust manifold usually means bad /clogged cats
Air entering the exhaust system (broken cats) usually means bad AFR cuz O2 sensor reads more O2 and it turns ECM commanding more PW for injectors.

[QUOTE]Before this all happened I did a 9th injector delete so it sat for a week before it was all done and now it's having all these issues. [QUOTE]

Do you re tune your ECM for the cold start valve delete,you need new upgraded cranck fuel pulse width tables on your tune.You can't just remove the cold start valve.

[QUOTE]I had a few codes that popped up. Mass Air Flow Malfunction (a new MAF did not fix my issue), Knock Sensor Malfunction (I rewired it so it was much further from the spark plug wires, did not fix my issue), TPS malfunction (I have had NO time to fiddle with this one), Burn Off Relay (swapped relays and no change, I did purchase two new relays for MAF power and burn off) [QUOTE]

All these codes are related each other.

First ceck the TPS using a voltmeter,set TPS at .54 volts with mechanical idle at 500 rpm (see the FSM for this setting)

Stephenms

I replaced the TPS today and my issue is still there. I noticed it starts to run like crap when smoke starts coming from the cats themselves. Which tells me clogged cats could be my culprit. This weekend I have some extra time so I will be unbolting the middle part of the exhaust just to test this theory lol. I'll keep you updated.

EDIT: I did more inspecting and research on my converters. I noticed in order to cut these cats I will have to weld a pipe. Clamps will not work due to the pipe going from a bend straight into the cat and a slight bend to the left after the cat.

Has anyone used that flex pipe from the auto part stores? I hear it's junk.

tunedport85inject

Clogged cats usually made glowing exhaust manifolds,the car runs like crap...before throwing parts you have to be sure...a new cat can solve your issue...if the cat is your issue...

Do you set the TPS as the FSM says? do you know about the procedure?

Stephenms

The TPS was set properly, yes. .52 volts.

As soon as my catalytic converters start to release smoke, the car runs like crap. It happens about two minutes after start up. A new Y pipe is about 350 bucks, which I do not have right now. It certainly would be easier to just get a new pipe, unbolt and bolt back on, but funds are tight.

Tom454

Can you disconnect at the cats and run it with just the y just for a test?

Stephenms

The cats are welded to the y-pipe. The only place it can be unbolted is at the exhaust manifold or at the muffler.

I looked online for a pipe and I found some reasonable prices, the only weird thing is that the O2 sensor is on the passenger side, mine is on the driver side.

Stephenms

Today I removed all three of the catalytic converters. The front two were clogged up in the middle and the left side had broken apart and turned sideways. The third one was broken apart too.

Better breathing, better throttle response, throaty sound, but still no fix to my issue. I actually got a whole day to sit and just diagnose it. Wrote wiring harnesses down on blank sheets of paper and went up and down the car.

I came to a realization: The temperature sensor relays the vehicles temp when the ECM asks for it. At start up, the computer knows to leave the pulse width long to warm up the car faster. As the computer sees temperatures rise into running temp is closes that pulse width gap. So, if the fuel pump is being told to full pump at start up it won't show it's ugly face. Once that pulse width drops to normal temp and timing is back at 6degrees, if the fuel pump can't perform properly it'll be noticed because the computer is requesting less fuel, cause the pump not to spin as much and finally showing it's true colors.

With that being said, if I disconnect the temp sensor while the car is at running temp, the computer will go to default and assume it's running cold which means it'll spin the fuel pump more. It'll use a lot of gas but if my issue goes away or gets better than I have my answer of the fuel pump.

Any idea if I'm on the right track?

tunedport85inject

do you check the fuel pressure?Basic tools for a TPI engine are a digital voltmeter,a test light,noid light for injectors pulse,a fuel pressure gauge,a timing light gun.That's all you need for basic tests.Now you could see how much pressure is running while you have that crap running engine.Put a fuel pressure gauge on the rail valve and see if you have a steady 40-43 psi with vacuum disconnected at pressure regulator.If you have steady pressure you have a good pump and regulator.With key on (engine off) you can test fuel pressure for 40 psi.You need steady pressure for about 15 minutes this confirms good fuel pressure regulator diaphragm and no injectors leaking.I'm confident you'r almost there,just some little steps...

Alberto-Italy

Stephenms

I do appreciate it!! I will be putting a Delphi OE pump with strainer on hold at work so if I need it I have it ready to put in. I will need to find a fuel pressure tester. One of the tools I don't have even though this should have been the first thing to check.

The pressure regulator IS new. Replaced about half a year ago. The old one was leaving me with rough starting issues because the ripped diaphragm would leak fuel into my vacuum lines. Replaced and adjusted properly.

Fuel injectors were not tested when I had them all out but the o-rings were replaced, upper and lower.

Fuel filter was replaced a year ago but I might as well do it again since I'm getting a new pump. I just hope I don't have rust in that tank. I went through four pumps in a 91 Z28 I had because of rust in the tank. First three were Airtex so I assumed crap parts lol.

Stephenms

I am beyond frustrated with this car!

New Delphi fuel pump and strainer was not the fix along with catalytic converters misplaced.

Next on my list is the fuel filter and check the injectors and look for kinked lines.

During road test it still hesitates on acceleration, won't accelerate once I hit 55 until it upshifts from a hard acceleration, basically feels like it's starving for fuel at that speed, a backfire once I floored it at low RPM.

Car starts right up since the new pump was installed but other than that it's still running hot and lean. It gets worse as temperature increases. Fuel pressure is okay at 45 psi but I did not brap the throttle, will be doing another running test soon.

Any new ideas? I talked to another mechanic who works on hot rods and classic cars. He said it is most likely a fuel issue.

What I'm thinking is, the hesitation is always there but since it idles so high at start up till it reaches temperature it's not noticed.

Cliff Harris

The ECM monitors the coolant temperature all the time. Almost everything related to the running of the engine is based on coolant temperature. Mainly that means injector pulse width and ignition advance.

The fuel pump has two speeds: on and off. The ECM will turn on the fuel pump while it sees DRPs (Distributor Reference Pulses) from the ignition module inside the distributor. The ignition module puts out DRPs any time the engine is rotating, which includes cranking and running. The only thing related to temperature that changes pulse width is the injectors.

If the coolant temperature sensor is disconnected while the engine is running the ECM will think the coolant temperature is -40° (F or C, take your pick). It will make the engine run very rich and idle at about 1200 RPM.

tunedport85inject

take a look inside the tank for grime that may have clogged the fuel filter...
new pump,good pressure and an hesitating car...clogged filter?how many miles on that fuel filter?was it ever changed?Hold on....

Stephenms

I did inspect the tank pretty well and didn't see anything that would damage the new pump. That pump I removed was original so I might as well have replaced it. Better now then wen it leaves me stranded.

As for the fuel filter, I replaced it about a year ago with an ACDelco filter.

I bought a new vacuum gauge and a fuel pressure tester so I'll be diagnosing after work today. I'm also going to try disconnecting the vacuum controlled fuel pressure regulator to see if my issue is with that. The regulator was replaced about half a year ago.

EDIT: I redid the vacuum test and my vacuum reading is 19 at start up and drops to 14 at idle. The idle is steady and when I tick the throttle it drops like normal and goes back to 14 and stays steady. When in drive it is sporadic due to missing.

That's telling me the timing is off. It's set to 6 degrees though, maybe it's unhappy with that? I'll have to inspect further. Much easier with the proper tools.