Loosing power @ WOT above 3000 RPM - need help

[KK6695GT]

I have this over in the 94-95 section but thought I'd try it over here and see if I have any better luck...........

Looking for some diagnostic help on my ’95 GT 93,000 mile 5.0 motor with a stock intake system (except for K&N filter) and a Mac shorty / Flowmaster cat-back exhaust. In other words, a basically a stock original motor w/o many mods.

The car runs great except above 3000 RPM at wide open throttle. About 2000miles ago I had some intermittent starting problems so the fuel pump, idle air control valve, ignition control module (not the computer), ignition coil, and fuel filter have all been replaced. (Replacing the ignition switch finally fixed the problem….). The car has been fine up to about a month ago.

For normal everyday driving the car is fine. If you run it up to 4500 at part throttle it’s fine and it will run continuously (cruise) at 4500 without a problem. It’s when you punch it and try to rev it above 3000 RPM that it has a problem. In other words, it will run up to 4500 fine with a part throttle but if it’s WOT (floored from a take off) it will run up to 3000-3500 RPM and then act like it’s running out of fuel above approximately 3000 RPM. It will start to die and loose power at 3000-3500 but momentum will carry it up to about 4500 (starts acting up about 3000 but will still rev up to 4500) but by then it’s dying enough to slow itself back down. If you hold it WOT it will continue to slow itself back down just like it’s running out of fuel. If you back off to part throttle at any point it’s fine and will run at 3000, 3500, 4000, what ever you want, but as soon as you step back down to WOT it acts like it’s loosing it’s fuel flow and begins to die again. I really don't believe it's a fuel issue though so the best way to describe it is to say it feels just like a rev limiter is kicking in or the advance is being pulled waaay too far forward or something. It's like it's a rev/vacuum controlled type issue.

No check engine light is showing and the fuel pressure regulator seems to be operating ok (I have a fuel pressure gauge mounted on the rail and at idle the PSI bumps up with the vacuum line disconnected like it should). With a new fuel pump and fuel filter, new ICA, and new ICM in the car and the regulator appearing to work I don’t really know where to go from here. It strikes me as a computer control/signal issue or some sensor like maybe the throttle position sensor type issue. I just hate to just throw money at new parts (particularly the computer) and hope something fixes it.

Anyone had this problem and know how to fix it!

Thanks.

 

[jrichker]

Dump the codes and see what the computer says is wrong… Codes can be present without setting the Check Engine Light.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

 

[TENGRAM]

most codes do not cause the CEL to illuminate. Check for Codes

 

[KK6695GT]

Sorry my fault, downside of trying navigate two threads at once........

I did get two codes, a 33 and a 133, neither of which I could identify. I'll look thought the site you gave and see what I can find for a reference.

Here's what I had posted as a response in the other:

The car is a mainly a weekend/after work driver and I'm not always driving it hard each time I take it out so it may go for awhile before I actually take notice/remember that it's acting up again and I need to do something about it. It's one one those remembering what it did this time vs last time deals so my memory of the specific conditions gets a little fuzzy.
But answering your question, it seems to do it hot or cold although I'd say more when it's cold. Also, I can't say that it necessarily does it every time I rev it WOT, but it seems like most every time.......

Also, when I try to get the OBD KOEO codes, using the check engine flash method I get a very faith flash, then a three and a three, a 4 second pause and then a one, three, and three. I don't have any codes shown in my books or CD referencing a 33 or a 133 code.

 

[jrichker]

The 33 code is valid for earlier 5.0's, but it is only 2 digits. If my memory is correct, the 94-95 cars have 3 digit codes. That would mean that this code reading is incorrect. If not, here is the code definition for 33.

Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal flickers. Remember that the computer does not source any power, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1 ohm.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif


EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in 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 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 5in 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 RPM.
should read about 5in vacuum

The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.

 

[KK6695GT]

Can't identify the 133 code but the 33 appears to be "insufficient EGR". Possibly the first 33 is the on-demand code and the 1 is just a separator code and then I'm getting a second 33 for the continuous code?

Didn't have the 33 on my code list, thanks for the copy you sent! Hopefully that's what it means. I'll assume so.......

Anybody know what the 133 might be or do you all think it's a 1 and then a 33? I believe it's a 133 because there wasn't a pause between the 1 and 3 and 3....

Before I go spend the money on a new one, anyone know if a bad EGR valve will cause the issue of loosing power at WOT above 3000 RPMS???

My MAC headers did have the tube fitting and I did connect them to the EGR with the stock tube. Anyone heard of any EGR issues with MAC shortube unequals?

TX

 

[JChalfan]

A cheap code reader might get you better results, since it sounds like you aren't getting good results by counting flashes.

You said you replaced the ignition coil... Do you have another coil you could swap in to rule that out? It kinda sounds like a possible ignition problem.

For what it's worth, I had the identical problem in a 1990 BMW 5-series I used to own. WOT it would cut out around 3k, but part throttle I could take it to redline. It turned out to be a spark plug I had dropped. The plug looked fine, but it put a little crack in the ceramic part right at the base. When I went WOT, the spark was jumping through the crack and that cylinder was cutting out.

Jeff

 

[KK6695GT]

Thanks JRichker, think I was typing at the same time you were so I missed your post.

I'll try the EGR tests. Thanks!

PS, Never dealt with a bad EGR before, any idea if that would cause my problem?

TX

 

[KK6695GT]

Coil could always be a possibility but usually they're a go/no-go type item. I had a hard time getting myself to buy one last year but I replaced it figuring you never know. I'll probably hold off on that for right now.

Plugs and wires (Mallory 8MM) are only about 2 years old but maybe got damaged putting the headers on? Holding off on spending money for new ones right now but may have to in the process of trouble shooting .........

 

[JChalfan]

The plugs could have been damaged installing headers. I usually remove plugs when I put on or take off headers so I don't break a plug.

I had a coil go out years ago on one of my carbureted cars, and I seem to remember that it started out by missing at high RPM's. I wouldn't suggest buying a new coil, but if you have a buddy you could borrow one from, that would rule it out as a possible cause.

Jeff

 

[HISSIN50]

The 33 code is valid for earlier 5.0's, but it is only 2 digits. If my memory is correct, the 94-95 cars have 3 digit codes. That would mean that this code reading is incorrect.

Correctimundo.

I think the 3 digit codes are kinda hard to read - the pulses are hard to detect. I run them a couple times to get a consensus. This is where the Midway Auto reader that JR links to can really be helpful.

I also know of no 133, so I'd try again.

Good luck.

 

[KK6695GT]

The 94-95 has the OBD-1 and the 96 and later are OBD-2 correct? I believe the OBD-1 is also refered to as an EEC-IV (compared to the OBD-2 as an EEC-V) in my Haynes manual.
Both the code charts that were posted show 2 digit codes for the EEC-IV (even though my Haynes manual only shows 3 didgit numbers) so wouldn't that imply that there are 2 digit codes for the OBD-1/EEC-IV and the 33 could be a good code?

 

[Daggar]

I do not recall the split in year between two digit and 3 digit codes but what I do remember is that NO Ford EEC puts out both types. You have either one or the other.

Not sure if that is helpful to you or not.

 

[TENGRAM]

The 94-95 has the OBD-1 and the 96 and later are OBD-2 correct? I believe the OBD-1 is also refered to as an EEC-IV (compared to the OBD-2 as an EEC-V) in my Haynes manual.
Both the code charts that were posted show 2 digit codes for the EEC-IV (even though my Haynes manual only shows 3 didgit numbers) so wouldn't that imply that there are 2 digit codes for the OBD-1/EEC-IV and the 33 could be a good code?

86-93 are 2-digit codes, 94-95 are 3-digit codes. also, there is no code 133. i suggest to try again per these instructions, or buy a code scanner, as the 3-digit codes are a bit harder to read.

 

[KK6695GT]

Well I guess the upside is this means I don't need to spend 80 bucks on a new EGR valve!
I'll try to run over to Autozone tomorrow or Weds and try using their reader and see if I can get a good reading.

 

[KK6695GT]

EGR appears to be ok. I pulled the vac line and operated it manually and that caused a fault code. Doing that helped me finally figure out the codes!!!

I've been reading the 3 3 1 3 3 as a two digit 33 code with a 1 for a separator. It's actually a 111 111 1 111 111. The pauses are alot shorter than the book descibed them. When I got the 334 for the EGR fault that I created by disconnecting it, it let me see how quick the 3 and 4 actually flash. 111 IS A PASS CODE. So as far as the computer is concerned, whatever is causing my problem apparently is not showing up in the computer.......

 

[KK6695GT]

I put new plugs in this weekend. Didn't help. Someone suggested plug wires but I really don't think it's that. The MSDs are not that old and they're the good Heli-Core (solid-wire) ones. Boots all look ok. It's just real hard to believe they've gone bad this quickly.

The thing that doesn't make sense in terms of being wires is that the car will cruise along fine at 3500, 4000, 4500 whatever, with no problem. If it was wires or something actually physically broken, I wouldn't expect it to run smooth like it does any time except WOT. Whenever I floor it and go to wide open throttle then it starts to bog. Let back off, it's fine.

 

[JChalfan]

ttt

I'm curious what this ends up being, anyone have any more suggestions?

For the heck of it, start your car up at night when its dark. Pop the hood and see if you have sparks jumping out of the wires or anything weird like that.

Jeff

 

[KK6695GT]

bump

 

[90bluegt]

I have a dumb thought, what GAP did you put your plugs at? It almost sounds like your losing spark or something at WOT after 3000 - 4500 RPM's. Perhaps the air rushing in is blowing out the spark before it gets to ignite (sp.)