RPM Problems

deaclen · 09-22-2005, 08:46 PM

A buddy of mine just gave me his non turbo-ed 86 Supra. I don't know much about these cars and i generally work on domestic vehicles. Any way i was wondering if you guys might have an idea of what would cause a vehicle not to go over 2500 rpms. I though maybe it has a built in rev limiter that is malfunctioning. A bad sensor, bad computer, not enogh fuel and a few other things. My bud already pulled the engine out of it though so i don't know for sure until i reinstall it. I did not think it was going to be neccessary for him to do that but oh well we shall see. Let me know what you guys think. NE and all help would be most appreciated.

rnoswal · 09-23-2005, 02:14 PM

Well, it could be timing, either cam or distributor. It could be a clogged fuel filter too. Make sure the butterfly is opening all the way and that there is nothing clogging the intake anywhere. Was it missing or running smmoth but just not revving up?

The cams and pistons are non-interference so they could be set wrong and still run but very poorly. Oh yeah, a clogged exhaust could cause that too, especially the cat. converter. Let us know.

Russ

WiseAssJester · 09-24-2005, 12:16 AM

Is the 7m a non-interference motor in that a piston at TDC wont slap a valve in its complete open position?

rnoswal · 09-24-2005, 06:30 AM

Yeah, that's it. The valves won't catch each other nor will they contact the head if the belt breaks. It is a nice feature, but it does mean there is room for a compression improvement either with the head or with high compression pistons. Of course then you will give up that safety margin, but the extra power may be worth it.

Russ

suprra_girl · 09-24-2005, 02:43 PM

not going over 2500rpm = limp home mode

timing belt jumped... ign timing way off

along those lines more than likely

monkihead · 09-26-2005, 07:38 PM

have you checked for vaccum leaks?? try by the head/manifold gasket & injector rubber o-rings. mine was loose by two bolts did the same thing.

khanh1315 · 10-05-2005, 06:35 AM

You should check your TPS. Try cleaning it or replace a new one. if tps is not good, rpm wont go over 2500rpm

rnoswal · 10-05-2005, 04:16 PM

So what did you find?

Russ

robbie · 10-11-2005, 12:11 PM

i have had same problem it will stutter a bit then sit on 2500 the more u accelerate the lower the rpm goes ....... the only way to stop it without replacing n e thing was to turn off the car and re-start i wasnt too shure what solved my problem after i had a full service but my money is on your throttle position sensor ... give it a thorough clean and check your fuel filter.....

mrnickleye · 10-13-2005, 04:26 AM

A plugged exhaust will cause an engine to not rev past a certain point. I repaired (replaced cats and mufflers) many on the 22R engine from the late 70s and into around 86 Celicas and trucks. Not many supras, but a posibilty.

09-22-2005, 08:46 PM	#1
deaclen Stock Join Date: Sep 2005 Posts: 1	RPM Problems A buddy of mine just gave me his non turbo-ed 86 Supra. I don't know much about these cars and i generally work on domestic vehicles. Any way i was wondering if you guys might have an idea of what would cause a vehicle not to go over 2500 rpms. I though maybe it has a built in rev limiter that is malfunctioning. A bad sensor, bad computer, not enogh fuel and a few other things. My bud already pulled the engine out of it though so i don't know for sure until i reinstall it. I did not think it was going to be neccessary for him to do that but oh well we shall see. Let me know what you guys think. NE and all help would be most appreciated.

09-24-2005, 02:43 PM	#5
suprra_girl 7M POWAH! ;) Join Date: Jun 2004 Location: New Zealand Posts: 2,312	not going over 2500rpm = limp home mode timing belt jumped... ign timing way off along those lines more than likely __________________ Please use the forum to ask your questions as they will get replied to much faster than pming me Pics of my build. "Good girls are just bad girls that don't get caught" Do a diagnostic first!

09-26-2005, 07:38 PM	#6
monkihead SP58GT Join Date: Mar 2005 Location: San Antonio texas Posts: 646	have you checked for vaccum leaks?? try by the head/manifold gasket & injector rubber o-rings. mine was loose by two bolts did the same thing. __________________ ....all you need is a small taste of success and you will find it suits you.... monique- better off dead

10-05-2005, 06:35 AM	#7
khanh1315 Stock Join Date: Oct 2005 Posts: 1	Tps bad You should check your TPS. Try cleaning it or replace a new one. if tps is not good, rpm wont go over 2500rpm

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Want to buy a Supra, though having some problems finding one.	Cypherbku	MKIV Supra	3	03-03-2009 01:45 AM
problems problems problems....	86SupraMan	MKIII Supra	5	02-04-2008 04:28 PM
Starting problems and accleration problems!	alekjame22	MKIII Supra	6	03-17-2007 11:19 PM
Oil leak problems	adellicson	MKIII Supra	1	03-04-2007 10:11 PM
problems, problems, and problems	tone loc	MKIII Supra	6	09-06-2006 04:35 AM

09-23-2005, 02:14 PM	#2
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	Well, it could be timing, either cam or distributor. It could be a clogged fuel filter too. Make sure the butterfly is opening all the way and that there is nothing clogging the intake anywhere. Was it missing or running smmoth but just not revving up? The cams and pistons are non-interference so they could be set wrong and still run but very poorly. Oh yeah, a clogged exhaust could cause that too, especially the cat. converter. Let us know. Russ

09-24-2005, 12:16 AM	#3
WiseAssJester 3" Exhaust Join Date: Sep 2005 Location: Reno Posts: 77	Is the 7m a non-interference motor in that a piston at TDC wont slap a valve in its complete open position?

09-24-2005, 06:30 AM	#4
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	Yeah, that's it. The valves won't catch each other nor will they contact the head if the belt breaks. It is a nice feature, but it does mean there is room for a compression improvement either with the head or with high compression pistons. Of course then you will give up that safety margin, but the extra power may be worth it. Russ

10-05-2005, 04:16 PM	#8
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	So what did you find? Russ

10-11-2005, 12:11 PM	#9
robbie Stock Join Date: Oct 2005 Location: in my car Posts: 2	i have had same problem it will stutter a bit then sit on 2500 the more u accelerate the lower the rpm goes ....... the only way to stop it without replacing n e thing was to turn off the car and re-start i wasnt too shure what solved my problem after i had a full service but my money is on your throttle position sensor ... give it a thorough clean and check your fuel filter.....

10-13-2005, 04:26 AM	#10
mrnickleye 1000whp postwhore Join Date: Jun 2005 Location: Mojave Desert, Calif. Posts: 1,705	A plugged exhaust will cause an engine to not rev past a certain point. I repaired (replaced cats and mufflers) many on the 22R engine from the late 70s and into around 86 Celicas and trucks. Not many supras, but a posibilty.