89 5.0 pinging, tourble starting when hot

jb89coupe · Sep 3, 2004

89 5.0 pinging, trouble starting when hot

Hi, maybe you guys can help me out...
My car is an 89 5.0 coupe ssp, mostly stock (k&n, exhaust, sus). It's been running strong since I got it, but suddenly started having some problems about a week ago. There's a lot of pinging/power loss under load, and the thing doesn't want to start when it's hot. Still starts right up and runs like a champ when it's cold.
I pulled the codes and got 22/23 in koeo (bap/tps), and passed the koer test. I've since tested and replaced both sensors and reset the computer - it resolved the codes, but had no effect on the problems.
Both issues came about at the same time (overnight, litterally) so I'm pretty sure they're related. I've replaced the rotor/cap, cleaned the tps, throttle body, bypass valve, and air filter - it got rid of some hesitation but no change on the pinging. I also just backed off the timing a bit down to 9* (it was running fine at 14* on 93oct), no change.
Any ideas why these symptoms would just appear suddenly, or advice on what to check next? BTW I've been through several tanks of (different) gas since this started.

Thanks in advance

jb89coupe · Sep 3, 2004

bump.

btw op.temp is 170-190f - pinging or starting trouble don't occur before it's up to temp. Someone's got to have a clue why bad pinging would appear all of a sudden in an otherwise healthy car? Is there something stupid I'm overlooking? (wouldn't be the first time)

Fastcat · Sep 3, 2004

When you say trouble starting do you mean it TRIES to start normally or it turns over really really slow? If it turns really really slow you have a timing issue. It it turns over normally but doesnt start you PROBABLY need to change your spark plugs

HISSIN50 · Sep 4, 2004

how is your Fuel pressure doing, especially when the motor is hot and you are pinging?
MAF wire clean? ECT test appropriately (it can be within absolute spec - no code - but not correct for the situation [out of calibration]).

please provide as much info as possible - stuff like this can be a wild goose chase.

good luck.

86/92stang · Sep 4, 2004

Possibly Dirty maf element? Maybe old(worn) battery/starter cables. Also may just be because of the heat and the older style starter. Possibly upgrade to a mini starter

1986LX2002 · Sep 4, 2004

check the spark plugs?? Usually you can tell by the condition of the plug whats wrong either normal wear or something has gone haywire. Also check the plug gap. Also with the TPS did you just install it or did you set the voltage as close to .99 as you could?

sjhm9102 · Sep 4, 2004

timing

jb89coupe · Sep 4, 2004

Thanks for the replies, I'll answer them in order..

It turns over like normal when it's hot, just doesn't want to start. I could just be jumping to conclusions about the 2 symptoms being related, maybe that's just my starter going bad.

I don't have an in-car fuel pressure gauge, so I can't see what it's doing when it starts pinging. I've tested it while priming and idling and it came out to specs. This was before the pinging started though, so I might do it again or just pick up a gauge. It seems like if it were a fuel issue the problem would be present all the time instead of just when hot? As for the ECT sensor, I'm not sure how to test that. Alldata gives a range (.3-3.5v), but nothing more specific to go by.

The MAF sensor and screen are among the things I've cleaned, even swapped the sensor with a friend, no change. I got the TPS in the mid-upper .9's (my meter's not that great), but from what I've read the computer adapts to whatever it reads during idle (after a reset) so it's not that important. Is that wrong?

I haven't gotten around to checking all the plugs, I was going to do that when I change them this weekend. I pulled a couple out before and it looked like normal wear, although they were gapped pretty wide (64ish), stock coil+dist. Maybe I'll find a bad one in there.

Like I said I recently backed the timing down to 9* from 14* (it's been running fine at 14 since I got it). I even brough it down further to 4* yesterday, the pinging gets better but it seems like I'm just masking the problem by doing this. Also with a can of octane booster added to 93 at 9* the pinging goes away except under extreme load (wot up a steep hill), but I shouldn't need to do that...

I just found a post in the forums from a while back about a faulty ACT sensor causing pinging and not showing an error code, I'll look into this too.

Thanks again, this place is a great resource.

jrichker · Sep 4, 2004

Pinging is caused by a number of things:
1.) Hot spots in the combustion chamber such as carbon deposits from high mileage or excessive oil consumption.
2.) Wrong heat range on the plugs.
3.) Too much initial spark advance.
4.) Lean fuel mixture.
Lean fuel mixture breaks out into several sub categories:
A. Vacuum leaks
B. Air entering the intake without passing through the MAF
C. Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D. Defective/missing EGR system: The EGR opens at cruse, dropping combustion temperature. The computer adds timing to compensate for the slower burning mixture. If the EGR is non-functional, the result can be pinging.
E. Clogged fuel injectors.
F. Fuel injector wiring problems causing injector not to deliver rated flow.
5.) Computer problems: (computer problems are not common like sensor problems)
A. ROM has bad data in fuel or timing table. This should also set a code in the computer.
B. Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one.

jb89coupe · Sep 7, 2004

pinging...

Well... changed the plugs (al ap25s) and wires (fms) over the weekend. The pinging seems to have gotten a little better - it doesn't sound like it's going to explode when cruising up a hill at 200* anymore, but it's still there. I threw in some fuel system/injector cleaner in recently, played with the timing some more (7-8-9-10*), checked for vacuum leaks, still using 93oct.. and I've already swapped all the sensors in the list above to no avail..
What's left? I don't know how to check the EGR system, so I can't rule that out, and I already know my computer to be bad, but I swapped with a friend and it still pings with his is it. (the computer's a whole 'nother story...)
Also keep in mind that this started suddenly - the car was running great at 16* since I got it, and now I can't seem to keep it from pinging...

Any more ideas, or advice on how to check my EGR system?

HISSIN50 · Sep 7, 2004

EGR introduces spent (inert) gasses at cruise. this dilutes the mixture and cools the chambers - which allow the puter to bring in a lot more timing. so if the system fails and does not introduce the spent gasses, the arguably hotter chambers and (mainly) ton of extra timing causes pinging.

JR knows the formal testing methods. i would apply some vac to the egr vac fitting while the car is idling - if the idle degrades or it stalls, the egr is atleast closed at idle. there is the solenoid (EVR) which gets puter input and opens to allow vac and energize the valve. the solenoid can malfunction. the egr valve itself can clog up and stick - cleaning it so the pintle moves freely can help in some situations.

if this is getting to you, and you have other puter issues, in the back of my mind (as a temp fix), one could run locked timing - a lot of SN guys have to do this to keep from pinging (detonation seems to be more intrinsic with their packaging and puter).

also as JR mentioned in his list a dirty MAF wire (or bad readings/wiring/connections) can cause pinging. just reiterating that, in case it was overlooked.
good luck.

jb89coupe · Sep 8, 2004

hmm.. would any of this egr stuff throw a code? my maf has been cleaned and swapped temporarily to no avail.
It seems like all the sensor cleaning/replacing, tuneup stuff, etc I've been doing since the pinging started has sort of masked it little by little, but I still haven't nailed whatever went wrong in the first place. Pretty aggrivating. But I think if I go a heat range colder on the plugs and get my car to run a little cooler for now I'll be fine. I've tried the locked timing and I couldn't get it to perform right, but it's a handy fix.

Anyway, thanks for the help guys. If anyone has more advice I'd be glad to hear it, but I guess I can get by just not mashing the pedal when it's hot for now, at least it's better than it was. Cooler weather is on the way, and I'm rebuilding in the winter - hopefully that'll get rid of the problem for good.

jrichker · Sep 8, 2004

Some theory on how the EGR works first and then the tests...

The EGR system has a vacuum source (line from the intake manifold), a computer operated electrical vacuum regulator, the EGR valve and the passages in the heads and intake manifold that route exhaust gas to the EGR valve. The computer uses RPM, Load. and some other factors to tell the vacuum regulator to pass vacuum to open the EGR valve. The EGR sensor tells the computer how far the EGR valve is open. Then computer adjusts the signal sent to the EGR vacuum regulator to hold, increase or decrease the vacuum.

The EGR shuts off at Wide Open Throttle (WOT), so it has minimal effect on performance. The addition of exhaust gas drops combustion temperature, increases gas mileage and reduces the tendency of the engine to ping.

Here’s an EGR test procedure I copied from cjones

to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5 in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPMs (remember snap the throttle don't hold it there).
did the vacuum gauge show about 5 in vacuum?

if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum, then connect vacuum gauge to the EGR valve side of the vacuum valve and snap throttle to 2500 RPMs.
should read about 5 in vacuum.

I typically use engine vacuum to do the first test. I use the spare vacuum port on the vacuum tree near the windshield wipers.

BlackGT89 · Sep 8, 2004

jb89coupe - I may have missed it but I didn't read if you have replaced your fuel filter yet. If not I would start by doing that. Also do you still have your original fuel pump ? I have an 89 also and I finally gave in and upgraded to a 190lph. You will probably also be surprised how much debris is in your fuel tank and maybe even on the sock filter. After a car warms up and demands are put on it would be the time a weak fuel pump would make itself known. You mentioned that you will be rebuilding soon and if you are stepping up your horsepower you will need to upgrade your fuel pump also. At the same time it would be good to get an adjustable fuel pressure regulator and a gauge (even an under hood type) as well so you know more about what your pressures are doing.

ninety15.0 · Sep 8, 2004

i agree check fuel filter and replace pump if need be. you should be running about 38 psi vac off. i had the same hot starting problem and it turned out to be the ground wire. I actually had to add a second ground from the battery to the block and it solved all of my starting problems. good luck man

BlackGT89 · Sep 8, 2004

ninety15.0 said:
I actually had to add a second ground from the battery to the block and it solved all of my starting problems. good luck man

Speaking of grounds, might even want to check this thread out.
http://forums.stangnet.com/showthread.php?t=499800
As old as these cars are it's probably not a bad idea to take all the ground wires loose and clean them thoroughly.

Daggar · Sep 8, 2004

One small note: Fuel injector cleaner that you dump into the gas is pretty much like pissing into the wind. Most all gas these days are detergent. If you suspect dirty fuel injectors you should probably remove them and take them to a place that has an injector cleaner --or-- my second choice would be to go to Firestone or someplace similar. There they have a can of cleaner that is hooked directly to your fuel rails and runs the car until empty. You'll be suprised how much 'junk' will come out of your tailpipes when that is done. By the way, the second method cleans not just the fuel injectors, but pistons, rings, valves, seals, rails, the works.

sweet~Low~93 · Sep 8, 2004

BlackGT89 said:
jb89coupe - I may have missed it but I didn't read if you have replaced your fuel filter yet. If not I would start by doing that.
.

Yup check fuel filter if you have not..
my dad's 93 5.0 would ping under load... [only 75k miles on the car]

got new filter and it runs so much harder now.. I think i could get a low or mid 14's out of it.
Vert. AOD , 373 gears, exhaust.. 1:7 rockers.

Let us know if that what happens. !

JimBowy · Sep 8, 2004

at work, subscribing...

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