Performance Loss Diag Help Needed - Pirate4x4.Com : 4x4 and Off-Road Forum

Injected · 07-12-2003, 08:58 PM

Hi
I’m looking for some help diagnosing a performance problem with my ’88, the specs on the Bronco are below. I’m also posting this on a couple of sites, so if you surf them you’ll probably see it elsewhere also.
I’ll start at the beginning, I was getting 10mpg after a recent rebuild of the 351 so I pulled the codes from the computer to see if I could find anything wrong. Upon running a KOEO test I pulled two codes, 34 and 41. I fixed the EGR problem (34), turned out that the bolt I used on one side of it was just a hair to long and was not pulling that side of the EGR valve to seat. I fixed it and got a good seal around valve, cleared the codes. Took it out for a drive, engine light comes on. Get back home and check codes, 41 is back. I also notice that my mid to upper power is gone but the lower end is a little (not by much) more responsive. Today I installed a new Oxygen Sensor, clear the codes and take it out for a 1hr test drive. Get back to the house to check the codes again (no engine light this time), everything is clean.
But I’m still down on power from what it was, starting around 2500rpm it just feels like someone threw the anchor out. Before all this it would kick up to a fast idle after getting on it and coming back down to stop and go traffic. And the power across the RPM range was impressive, now it sucks. I’ve not put enough miles on since the O2 sensor change to tell if my mileage is any better, I’m just really disappointed with the power I lost.
Do you think its EGR related? I Vacuum tested the EGR valve and it seemed to leak down a bit, but it may have been the vac line I used to test it with also. Other than that I made no other adjustments on the truck, and now it pulls way less in the mid to upper range. It used to jump and the engine would rev up faster, now it seems to take forever to work up the rpms with the same amount of pedal. Almost like someone is applying a trans-brake or something.
I know the power is in there, I need to find out where it went and what is affecting it. Any Ideas????????

Thanks,
Greg

1988 Bronco
C6 w/B&M Shift Kit
3.55 Gears
.040 351w
Ported Truck Intake
Ported E7 heads with 1.9in/1.6ex valves
Comp Cam P/N-35-255-5, Grind #XE254H-14,
http://www.compcams.com/catalog/162_163.html
LSA-114
Intake - .478
Exhaust - .485
Intake Dur @ .050 – 210
Exhaust Dur @ .050 – 214
Shorty Headers, no Cat, Flowmaster 80 Series with Two 2 ½” inlets, One 3” outlet
MSD TFI Module
Ford Racing 9mm wires
31” Dunlop Radial Rovers

maritime mudder · 07-12-2003, 09:19 PM

Are you sure your TPS is reading correctly? Mine had a similar problem and the inner plastic on the tps was stripped and not allowing it to follow the throttle plate correctly, I would not get a code as is was still operational and did read somewhat. Not sure if this helps or not but give it a try. Just test the voltage across the TPS as you open the throttle (engine off, key on) and compare it to spec.

Injected · 07-14-2003, 01:01 AM

Thanks, checked and swapped out the TPS after it checked out of range, got some of my power back but not all. Now I'm getting code 41 (system reads lean), and it's running really rich.

1uglyranger · 07-14-2003, 12:30 PM

This may sound stupid, but it's happened before. Did you remember to re-install your PIP? If you don't know what that is, its the little "chip" in-line with the ignition module. It will cause the computer to not be able to advance timing, which will allow low end power to be normal, but upper end to lag.

Also, throw a vaccum gauge on it, and see what it says at idle, cruise, snap throttle, and deceleration. Vaccum gauges can tell you a lot

Brian--

Injected · 07-14-2003, 04:29 PM

Yeap got everything put back together correctly, it's just weird that before with the EGR leak it would make soooo much more power.
Well i put a vac gauge on it and it reads 18" at idle, about 650-800rpm. When I rev the motor it dips to 15" then jumps up to 22". I noticed after it's been running that when I shut it down I can hear a buzzing sound coming from the EGR control solenoid on the drivers side of the engine, but it goes away after about 10-15 secs. That's the unit closest to the front of the vehicle in the group of three controls just to the drivers side of the coil. All three units are then hung on the valve cover as an assembly. This one is the closest to the front and has a round white plastic cylinder top. I did verify it is hooked up to the EGR with a vac line. It does not buzz when it's running, just when you shut it down after it's been running for a few mins.

Is this normal? or is it leaking down after I shut the motor off?

I pulled a vac line off the manifold just to test how it would react, idle raised but it smoothed out the idle and sounded like it used to before the EGR leak was fixed. Although I think the egr leak was less of a leak than the vac line disconnected.

1uglyranger · 07-14-2003, 10:06 PM

Do you have access to a 4-gas?

richenry · 07-15-2003, 05:38 AM

replace map sensor code lean 02 rich

Injected · 07-21-2003, 02:46 PM

Well I'm planning on putting it on a dyno as soon as I get some time to check the exhaust content.
I replaced everything and it still did it so I sent all the new parts back to my supplier and went back to the original stuff.
I did find the rough idle problem, it was a short in the O2 sensor grounding wire. Now it runs fine, but I still have a big power loss. I've narrowed it down to either worn out injectors or a torque converter/tranny problem. I'm waiting on an AFPR to play with the fuel pressure, but its well within the acceptable range as it stands right now.
This is my first Ford in over 15 years, I'm struggling a little with the speed density setup.
I've checked everything to solve the power loss but have come up empty so far, the motor tests excellent. All controls test OK, I'm thinking about throwing an extra AOD I have behind it soon to see if it is the T/C. The C6 has issues when it gets hot and has made some banging noise in the T/C on downshift, so I'm not ruling it out.
I'm hoping to get some time tonight to check the injectors, only because the drivers side plugs came out looking lean and the passenger side plugs looked just fine when I checked them yesterday.
I have a feeling I'm going to be changing injectors soon also, these look like they've seen some pretty hard miles.

Greg

07-12-2003, 08:58 PM	#1 (permalink)
Injected Registered User Join Date: Jan 2003 Member # 16159 Location: Mpls, MN Posts: 16	Performance Loss Diag Help Needed Hi I’m looking for some help diagnosing a performance problem with my ’88, the specs on the Bronco are below. I’m also posting this on a couple of sites, so if you surf them you’ll probably see it elsewhere also. I’ll start at the beginning, I was getting 10mpg after a recent rebuild of the 351 so I pulled the codes from the computer to see if I could find anything wrong. Upon running a KOEO test I pulled two codes, 34 and 41. I fixed the EGR problem (34), turned out that the bolt I used on one side of it was just a hair to long and was not pulling that side of the EGR valve to seat. I fixed it and got a good seal around valve, cleared the codes. Took it out for a drive, engine light comes on. Get back home and check codes, 41 is back. I also notice that my mid to upper power is gone but the lower end is a little (not by much) more responsive. Today I installed a new Oxygen Sensor, clear the codes and take it out for a 1hr test drive. Get back to the house to check the codes again (no engine light this time), everything is clean. But I’m still down on power from what it was, starting around 2500rpm it just feels like someone threw the anchor out. Before all this it would kick up to a fast idle after getting on it and coming back down to stop and go traffic. And the power across the RPM range was impressive, now it sucks. I’ve not put enough miles on since the O2 sensor change to tell if my mileage is any better, I’m just really disappointed with the power I lost. Do you think its EGR related? I Vacuum tested the EGR valve and it seemed to leak down a bit, but it may have been the vac line I used to test it with also. Other than that I made no other adjustments on the truck, and now it pulls way less in the mid to upper range. It used to jump and the engine would rev up faster, now it seems to take forever to work up the rpms with the same amount of pedal. Almost like someone is applying a trans-brake or something. I know the power is in there, I need to find out where it went and what is affecting it. Any Ideas???????? Thanks, Greg 1988 Bronco C6 w/B&M Shift Kit 3.55 Gears .040 351w Ported Truck Intake Ported E7 heads with 1.9in/1.6ex valves Comp Cam P/N-35-255-5, Grind #XE254H-14, http://www.compcams.com/catalog/162_163.html LSA-114 Intake - .478 Exhaust - .485 Intake Dur @ .050 – 210 Exhaust Dur @ .050 – 214 Shorty Headers, no Cat, Flowmaster 80 Series with Two 2 ½” inlets, One 3” outlet MSD TFI Module Ford Racing 9mm wires 31” Dunlop Radial Rovers __________________ "So you're saying listening to the voices is a BAD thing?"

07-12-2003, 09:19 PM	#2 (permalink)
maritime mudder Registered User Join Date: Nov 2001 Member # 8411 Location: Sussex, New Brunswick Posts: 92	Are you sure your TPS is reading correctly? Mine had a similar problem and the inner plastic on the tps was stripped and not allowing it to follow the throttle plate correctly, I would not get a code as is was still operational and did read somewhat. Not sure if this helps or not but give it a try. Just test the voltage across the TPS as you open the throttle (engine off, key on) and compare it to spec. __________________ HUH?

07-14-2003, 01:01 AM	#3 (permalink)
Injected Registered User Join Date: Jan 2003 Member # 16159 Location: Mpls, MN Posts: 16	Thanks, checked and swapped out the TPS after it checked out of range, got some of my power back but not all. Now I'm getting code 41 (system reads lean), and it's running really rich. __________________ "So you're saying listening to the voices is a BAD thing?"

07-14-2003, 12:30 PM	#4 (permalink)
1uglyranger Pirate4x4 Addict! Join Date: Aug 2001 Member # 6576 Location: Oakley, CA Posts: 6,109	This may sound stupid, but it's happened before. Did you remember to re-install your PIP? If you don't know what that is, its the little "chip" in-line with the ignition module. It will cause the computer to not be able to advance timing, which will allow low end power to be normal, but upper end to lag. Also, throw a vaccum gauge on it, and see what it says at idle, cruise, snap throttle, and deceleration. Vaccum gauges can tell you a lot Brian-- __________________ Brian Whitford 711 Dysfunctional Rockcrawlers Rage 4th............ "safety is our #2 concern"

07-14-2003, 04:29 PM	#5 (permalink)
Injected Registered User Join Date: Jan 2003 Member # 16159 Location: Mpls, MN Posts: 16	Yeap got everything put back together correctly, it's just weird that before with the EGR leak it would make soooo much more power. Well i put a vac gauge on it and it reads 18" at idle, about 650-800rpm. When I rev the motor it dips to 15" then jumps up to 22". I noticed after it's been running that when I shut it down I can hear a buzzing sound coming from the EGR control solenoid on the drivers side of the engine, but it goes away after about 10-15 secs. That's the unit closest to the front of the vehicle in the group of three controls just to the drivers side of the coil. All three units are then hung on the valve cover as an assembly. This one is the closest to the front and has a round white plastic cylinder top. I did verify it is hooked up to the EGR with a vac line. It does not buzz when it's running, just when you shut it down after it's been running for a few mins. Is this normal? or is it leaking down after I shut the motor off? I pulled a vac line off the manifold just to test how it would react, idle raised but it smoothed out the idle and sounded like it used to before the EGR leak was fixed. Although I think the egr leak was less of a leak than the vac line disconnected. __________________ "So you're saying listening to the voices is a BAD thing?"

07-14-2003, 10:06 PM	#6 (permalink)
1uglyranger Pirate4x4 Addict! Join Date: Aug 2001 Member # 6576 Location: Oakley, CA Posts: 6,109	Do you have access to a 4-gas? __________________ Brian Whitford 711 Dysfunctional Rockcrawlers Rage 4th............ "safety is our #2 concern"

07-15-2003, 05:38 AM	#7 (permalink)
richenry Registered User Join Date: Feb 2003 Member # 17436 Location: san angelo tx Posts: 4	88 bronco no power replace map sensor code lean 02 rich

07-21-2003, 02:46 PM	#8 (permalink)
Injected Registered User Join Date: Jan 2003 Member # 16159 Location: Mpls, MN Posts: 16	Well I'm planning on putting it on a dyno as soon as I get some time to check the exhaust content. I replaced everything and it still did it so I sent all the new parts back to my supplier and went back to the original stuff. I did find the rough idle problem, it was a short in the O2 sensor grounding wire. Now it runs fine, but I still have a big power loss. I've narrowed it down to either worn out injectors or a torque converter/tranny problem. I'm waiting on an AFPR to play with the fuel pressure, but its well within the acceptable range as it stands right now. This is my first Ford in over 15 years, I'm struggling a little with the speed density setup. I've checked everything to solve the power loss but have come up empty so far, the motor tests excellent. All controls test OK, I'm thinking about throwing an extra AOD I have behind it soon to see if it is the T/C. The C6 has issues when it gets hot and has made some banging noise in the T/C on downshift, so I'm not ruling it out. I'm hoping to get some time tonight to check the injectors, only because the drivers side plugs came out looking lean and the passenger side plugs looked just fine when I checked them yesterday. I have a feeling I'm going to be changing injectors soon also, these look like they've seen some pretty hard miles. Greg __________________ "So you're saying listening to the voices is a BAD thing?"

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