1988 7MGE Misfire - Stumped!

excaliburdj · 04-13-2008, 10:43 PM

I've read there are places that sell vacuum hose kits cut and sized to a particular model engine.

Any recommendations for a good place to get a hose kit?

cre · 04-14-2008, 12:30 AM

Last I checked I found no kits for the 7M-GE. There are kits for the 7M-GTE, but they've got more of the larger diameter hose than needed and are several feet short of the smaller diameters.

This page of the EPC lists most of the hose lengths in millimeters:
Vacuum Piping

This page lists some of the others which are in both models and covers which sizes are used where pretty well:
Cygnus X1 Home Page

4mm and 3.5mm are the sizes you'll end up short on if you go with a GTE kit.

excaliburdj · 04-14-2008, 10:55 PM

OK, did some more investigating after work tonight. I also replaced all the small vacuum hoses on the intake side of the engine. No change.

What I did find, however, was that it is cylinders 3 and 5 misfiring every time. I did the old "pull the wire off the distributor and see if the idle changes" trick, and I can remove both of those wires with no change at all in the idle.

Thoughts? What would connect these 2 cylinders?

cre · 04-15-2008, 02:08 AM

3 and 5? Nothing... unless there's a problem in the ECU or the igniter which is causing a precise timing problem.

You might try checking for oil or water down in the plug galleys... that can sometimes cause a short to ground.

excaliburdj · 04-15-2008, 02:27 AM

I know where the ECU is, but where do I find the igniter?

cre · 04-15-2008, 02:38 AM

It's mounted right under the ignition coil. Aluminum box.

excaliburdj · 04-15-2008, 03:07 AM

Ah...got it. I suppose that's a dealer only part? I found a used ECU on eBay, but igniters are probably pretty rare.

Have you heard anything about aftermarket coil/igniter packs? Accel makes one that's supposedly designed to replace both boxes, I think.

Or for a daily driver would you recommend just replacing the factory box itself?

cre · 04-15-2008, 03:24 AM

I don't know of anything by Accel which would replace both. MSD makes an electronic ignition which would though.... but it's costly and not a direct replacement.

Don't just start buying parts because you think it *might* be one thing or another... you'll be broke long before you fix anything.

Have you checked the galleys for oil or water?

How old is the cap (not the rotor) on the distributor? If the contact for 3 and 5 have a lot of carbon buildup they can loose spark as well.

As for the igniter, typically when that goes it's not consistent like you've found... personally, I'd keep looking for something else which would be causing problems. The igniter and ECU are possibilities, but they're remote possibilities.

excaliburdj · 04-15-2008, 03:54 AM

When I re-checked the plugs and wires I checked for fluids in the galleys. Cyl 2 had some, but I think it was from pulling the coolant hose off the intake and not having the rag in the right place to catch it all.

I even went so far as to switch the spark plugs that were in 3 and 5 to 1 and 2 to make sure it wasn't the plugs.

Nope...no change. Still 3 and 5 misfiring (or NOT firing, more accurately.)

The distributor cap is new. Just replaced it on Saturday to make sure that wasn't a problem.

Maybe I'll see if I can post a Youtube video of the engine idling or something. It's weird, because about 1/4 of the time it runs just fine, but I can't seem to tell what makes it kick in and out of that. It's not when it's warm, because sometimes it'll run fine from a cold start, and then kick in later with the misfiring.

I've been reading all day trying to figure out specifically what could be plugged/clogged/bad that would control the firing of the cylinders as opposed to an engine function like idling, and I'm coming up empty.

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04-13-2008, 10:43 PM	#1
excaliburdj Stock Join Date: Apr 2008 Location: Iowa Posts: 11	I've read there are places that sell vacuum hose kits cut and sized to a particular model engine. Any recommendations for a good place to get a hose kit?

04-14-2008, 12:30 AM	#2
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Last I checked I found no kits for the 7M-GE. There are kits for the 7M-GTE, but they've got more of the larger diameter hose than needed and are several feet short of the smaller diameters. This page of the EPC lists most of the hose lengths in millimeters: Vacuum Piping This page lists some of the others which are in both models and covers which sizes are used where pretty well: Cygnus X1 Home Page 4mm and 3.5mm are the sizes you'll end up short on if you go with a GTE kit.

04-14-2008, 10:55 PM	#3
excaliburdj Stock Join Date: Apr 2008 Location: Iowa Posts: 11	OK, did some more investigating after work tonight. I also replaced all the small vacuum hoses on the intake side of the engine. No change. What I did find, however, was that it is cylinders 3 and 5 misfiring every time. I did the old "pull the wire off the distributor and see if the idle changes" trick, and I can remove both of those wires with no change at all in the idle. Thoughts? What would connect these 2 cylinders?

04-15-2008, 02:08 AM	#4
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	3 and 5? Nothing... unless there's a problem in the ECU or the igniter which is causing a precise timing problem. You might try checking for oil or water down in the plug galleys... that can sometimes cause a short to ground.

04-15-2008, 02:27 AM	#5
excaliburdj Stock Join Date: Apr 2008 Location: Iowa Posts: 11	I know where the ECU is, but where do I find the igniter?

04-15-2008, 02:38 AM	#6
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	It's mounted right under the ignition coil. Aluminum box.

04-15-2008, 03:07 AM	#7
excaliburdj Stock Join Date: Apr 2008 Location: Iowa Posts: 11	Ah...got it. I suppose that's a dealer only part? I found a used ECU on eBay, but igniters are probably pretty rare. Have you heard anything about aftermarket coil/igniter packs? Accel makes one that's supposedly designed to replace both boxes, I think. Or for a daily driver would you recommend just replacing the factory box itself?

04-15-2008, 03:24 AM	#8
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	I don't know of anything by Accel which would replace both. MSD makes an electronic ignition which would though.... but it's costly and not a direct replacement. Don't just start buying parts because you think it might be one thing or another... you'll be broke long before you fix anything. Have you checked the galleys for oil or water? How old is the cap (not the rotor) on the distributor? If the contact for 3 and 5 have a lot of carbon buildup they can loose spark as well. As for the igniter, typically when that goes it's not consistent like you've found... personally, I'd keep looking for something else which would be causing problems. The igniter and ECU are possibilities, but they're remote possibilities.

04-15-2008, 03:54 AM	#9
excaliburdj Stock Join Date: Apr 2008 Location: Iowa Posts: 11	When I re-checked the plugs and wires I checked for fluids in the galleys. Cyl 2 had some, but I think it was from pulling the coolant hose off the intake and not having the rag in the right place to catch it all. I even went so far as to switch the spark plugs that were in 3 and 5 to 1 and 2 to make sure it wasn't the plugs. Nope...no change. Still 3 and 5 misfiring (or NOT firing, more accurately.) The distributor cap is new. Just replaced it on Saturday to make sure that wasn't a problem. Maybe I'll see if I can post a Youtube video of the engine idling or something. It's weird, because about 1/4 of the time it runs just fine, but I can't seem to tell what makes it kick in and out of that. It's not when it's warm, because sometimes it'll run fine from a cold start, and then kick in later with the misfiring. I've been reading all day trying to figure out specifically what could be plugged/clogged/bad that would control the firing of the cylinders as opposed to an engine function like idling, and I'm coming up empty.