Engine Foxbody idle/throttle issues

red5.0fox · Sep 11, 2023

TwoRockTwo said:
Not sure if you ever got the base timing set correctly, but start there.
-verify TDC, mark the balancer 0°
-if it’s not at 0° replace the balancer
-with the engine fully warmed up, pull the SPOUT and set timing to 10° BTDC. Make sure you don’t set it to 10° ATDC, both marks should be present. (12°-13° if you prefer)
-with a DVM, check TPS throughout its range & idle
-check fuel pressure w/ vacuum line off, should be 39#
-smoke test again. Again. Again.

If the issue still persists::
-remove the plugs and check condition for damage/ fouling
-just replace the ignition wires. They are hard to diagnose when having internal damage and that can occur often when pulling them off the plugs
-compression/ leak down test while you have the plugs out.

I'll recheck timing next time I have a chance. I have the injectors out right now, had them flow tested, and a few are looking pretty suspicious, so I plan on cleaning them. I have checked the TPS, it's set at .97v. I also checked the fuel pressure with the line off, and that's exactly what I got. The wires were replaced a few months ago with ford motorcraft wires, and the plugs to go with it, so I don't believe that's the issue, however, I will check for fouled plugs. I'll also do the compression test when I have it all back together. I'm currently an auto tech student, and my instructor has repeatedly told me "it just needs a tune", but for the first 6 months I had this exact setup, it ran beautifully, so I don't think it's "just a tune".

TwoRockTwo · Sep 11, 2023

It’s not a tune issue, it’s a fuel delivery or spark/ timing issue.

You need to verify the TPS voltage throughout it’s entire range, not just at idle. It must be smooth and continuous, steadily increasing in voltage up to approximately 4.9v-5.0v

Your teacher is doing you a disservice by blindly dismissing the issues.

Yes a tune would help, solve surging & stalling, but not the issue you have.

It’s the perfect opportunity for your teacher to teach basic troubleshooting.
A competent mechanic should be able to diagnose in an hour or less.

red5.0fox · Sep 12, 2023

TwoRockTwo said:
It’s not a tune issue, it’s a fuel delivery or spark/ timing issue.

You need to verify the TPS voltage throughout it’s entire range, not just at idle. It must be smooth and continuous, steadily increasing in voltage up to approximately 4.9v-5.0v

Your teacher is doing you a disservice by blindly dismissing the issues.

Yes a tune would help, solve surging & stalling, but not the issue you have.

It’s the perfect opportunity for your teacher to teach basic troubleshooting.
A competent mechanic should be able to diagnose in an hour or less.

Completely agree. It really upsets me because I keep getting put on the back burner, but it is what it is, I'll figure it out. I plan on getting these injectors cleaned today and we'll see what I can get put back together this evening. I'll be sure to check the TPS voltage throughout it's range aswell, just may be a couple days, but I'll keep it updated.

red5.0fox · Sep 12, 2023

I have cleaned 2 sets of injectors. One were the purple EV6 style injectors, which were in my car. They have 6 pinholes on the bottom, but they seemed to be spraying in 2 major lines. I then cleaned another set of greentop EV1 injectors, and they misted much more than the EV6 injectors. The greentops however have 2 broken caps, so I need to get those fixed. Could the EV6 injectors not "misting" as much be causing some issues?

TwoRockTwo · Sep 12, 2023

Yeah possibly.
You can buy replacement caps at your local parts stores fyi

But I don’t think that’s your issue.

I would reuse the EV1 injectors, but they sound like 42#, which is too big to use without a tune or at least a calibrated MAF meter to compensate for the extra fuel.

Not sure what size the purple EV6 are.

If you have the original 19’s you should use those

red5.0fox · Sep 12, 2023

TwoRockTwo said:
Yeah possibly.
You can buy replacement caps at your local parts stores fyi

But I don’t think that’s your issue.

I would reuse the EV1 injectors, but they sound like 42#, which is too big to use without a tune or at least a calibrated MAF meter to compensate for the extra fuel.

Not sure what size the purple EV6 are.

If you have the original 19’s you should use those

I researched both injectors, and can confirm they are 24#. The purples are Ford Racing injectors which can be found on LMR, and the green are ford branded, can't confirm what # they are though. I have a ton of 19# injectors out of lots of different things, but they have all seen better days. Cracked caps, bad o'rings, etc. I don't even know if half of them work lol. I'm gonna toss the purple ones back in since I know they work. Getting ready to do that right now, I'll update with what happens.

red5.0fox · Sep 12, 2023

TwoRockTwo said:
Not sure if you ever got the base timing set correctly, but start there.
-verify TDC, mark the balancer 0°
-if it’s not at 0° replace the balancer
-with the engine fully warmed up, pull the SPOUT and set timing to 10° BTDC. Make sure you don’t set it to 10° ATDC, both marks should be present. (12°-13° if you prefer)
-with a DVM, check TPS throughout its range & idle
-check fuel pressure w/ vacuum line off, should be 39#
-smoke test again. Again. Again.

If the issue still persists::
-remove the plugs and check condition for damage/ fouling
-just replace the ignition wires. They are hard to diagnose when having internal damage and that can occur often when pulling them off the plugs
-compression/ leak down test while you have the plugs out.

I reset the timing. I put a paper towel in the #1 cylinder, and it blew out while I handturned the motor. However, the 0 degree mark is NOWHERE near the timing pointer. Do I need a balancer?

General karthief · Sep 12, 2023

Blowing air out the spark plug hole is not finding TDC. You can feel the air coming out that's the compression stroke, I use a small long screw driver, feel for the top of the piston (gently), it will stop, then move down, go back till it stops, fine line between up and down, balancer should be at 0* , rotor at the #1 spark plug tower, if all that does not line up within a smidge then further investigation is needed, balancer replacement or distributor may be one tooth off, loose timing chain.
Computer controlled engines have a need for accurate events, even as archaic as the obd1 computer is.
Your shop teacher may be unfamiliar with our cars and generalizing with the new cars need to be 'tuned' (computer flash) to accommodate a wiper blade change. Forgive him.

red5.0fox · Sep 12, 2023

General karthief said:
Blowing air out the spark plug hole is not finding TDC. You can feel the air coming out that's the compression stroke, I use a small long screw driver, feel for the top of the piston (gently), it will stop, then move down, go back till it stops, fine line between up and down, balancer should be at 0* , rotor at the #1 spark plug tower, if all that does not line up within a smidge then further investigation is needed, balancer replacement or distributor may be one tooth off, loose timing chain.
Computer controlled engines have a need for accurate events, even as archaic as the obd1 computer is.
Your shop teacher may be unfamiliar with our cars and generalizing with the new cars need to be 'tuned' (computer flash) to accommodate a wiper blade change. Forgive him.

Ya its super annoying lol, especially because I know that isn't my issue. Before I quit for tonight, I had done the timing, and after the papertowel blew out I kept turning the engine until I got between 0-10 degrees BTDC, then I pointed the rotor at the #1 plug tower. Unfortunately, I couldn't get it started fast enough before the battery died. After charging, I got it started, it idled for about 30 seconds while I was rushing to grab the timing light (I had put it away), and it died before I got it out of my tool box. It's had that problem aswell, and it happens very randomly. Sometimes when I'd be sitting at a light, it would be idling fine, then just die. For the short time I had it running, giving it throttle, the same issue was present. I'll attach a video.

red5.0fox · Sep 12, 2023

General karthief said:
Blowing air out the spark plug hole is not finding TDC. You can feel the air coming out that's the compression stroke, I use a small long screw driver, feel for the top of the piston (gently), it will stop, then move down, go back till it stops, fine line between up and down, balancer should be at 0* , rotor at the #1 spark plug tower, if all that does not line up within a smidge then further investigation is needed, balancer replacement or distributor may be one tooth off, loose timing chain.
Computer controlled engines have a need for accurate events, even as archaic as the obd1 computer is.
Your shop teacher may be unfamiliar with our cars and generalizing with the new cars need to be 'tuned' (computer flash) to accommodate a wiper blade change. Forgive him.

okay, I can’t seem to post a video here. Anyways, when you give it gas (for example, 1/2 throttle) the RPM’s go up to about 1500-2000 rpm, then go straight down to about 600. It stays this way even under throttle. When you let off the throttle, it bounces back up then settles back down to idle. Hopefully this is well enough explained.

General karthief · Sep 12, 2023

red5.0fox said:
I kept turning the engine until I got between 0-10 degrees BTDC,

Ain't no 'in between ' it's got to be 0* then set distributor to 10-12* with the engine running, spout pulled of course.

AeroCoupe · Sep 12, 2023

If you are not sure if you have the motor up on TDC you can pull the passenger valve cover and if both valves are closed and the piston is rising then the motor is on the compression stroke. When the piston stops rising the motor will turn several degrees before the piston starts to move back down. You need to note where the pointer is on the balancer when it stops moving up and then when it starts moving down. Take the number of degrees between, divide by two, and add that to the mark at when the piston stopped moving up. This is TDC.

If the pointer is not pointing to 0 on the balancer then it’s most likely the outer ring on the balancer has moved and the balancer need to be replaced.

TwoRockTwo · Sep 13, 2023

The engine has to already be warmed up for you to time it properly, as in 200° or so., past the fuel enrichment and into closed loop.

Find TDC first, then warm up the engine, then pull the spout and set timing. Manipulate the throttle if you have to in order to get it warmed up.

And check that TPS, car doesn’t have to be running to do that, just turn on ignition.

TwoRockTwo · Sep 13, 2023

I prefer a physical means of verifying TDC, feeling the piston with a plastic straw, screwdriver, or a piston stop.

red5.0fox · Sep 18, 2023

General karthief said:
Ain't no 'in between ' it's got to be 0* then set distributor to 10-12* with the engine running, spout pulled of course.

OH, I gotcha! I've never set it that way so that may explain a lot of issues. I'll do it again this week and do it that way.

red5.0fox · Sep 18, 2023

TwoRockTwo said:
I prefer a physical means of verifying TDC, feeling the piston with a plastic straw, screwdriver, or a piston stop.

Usually this is how I do it, but I haven't had anyone to hold the screwdriver up there.

red5.0fox · Sep 18, 2023

TwoRockTwo said:
It’s not a tune issue, it’s a fuel delivery or spark/ timing issue.

You need to verify the TPS voltage throughout it’s entire range, not just at idle. It must be smooth and continuous, steadily increasing in voltage up to approximately 4.9v-5.0v

Your teacher is doing you a disservice by blindly dismissing the issues.

Yes a tune would help, solve surging & stalling, but not the issue you have.

It’s the perfect opportunity for your teacher to teach basic troubleshooting.
A competent mechanic should be able to diagnose in an hour or less.

I tested my TPS sensor while the vehicle was running. At idle I was at .98v, I had a friend rev up the car slowly all the way to 5k rpm and the most I saw out of the tps sensor was 1.19v

General karthief · Sep 18, 2023

red5.0fox said:
Usually this is how I do it, but I haven't had anyone to hold the screwdriver up there.

pull all the plugs, then you can turn the engine by hand with a breaker bar or long ratchet, hold your own screwdriver, your friend can hold your beer.
Oh, make sure the car is not in gear

red5.0fox · Sep 18, 2023

General karthief said:
pull all the plugs, then you can turn the engine by hand with a breaker bar or long ratchet, hold your own screwdriver, your friend can hold your beer.
Oh, make sure the car is not in gear

Ya, usually I just lay under the car with only the #1 plug out because I'm lazy and I turn the crank with a breaker bar lol. Usually my girlfriend is holding the screwdriver but she gets confused with feeling when the piston stops lol. So then we wind up switching and she turns the crank haha.

General karthief · Sep 18, 2023

Well that may award you with a CT, I need to call the janitor. @Noobz347 ................

Engine Foxbody idle/throttle issues

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wonder how much it would cost to ship you a pair

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wonder how much it would cost to ship you a pair

lube between the nut and the face. I know my lubes

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wonder how much it would cost to ship you a pair

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wonder how much it would cost to ship you a pair

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