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Lexuszeal
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6 Posts
Discussion Starter #1
Three months ago I bought a 1991 Lexus ES250 that idles low like it wants to stall. This low idle is more noticable during acceleration at low speeds and obviously when stopped. There is a brief time when put into gear and accelarating, that it almost stalls in order to die. I have only changed plugs to know if that would solve this problem; to no such luck.:thumbdown
Furthermore, Today, I disassembled the air cleaner; throttle body; intake manifold body; and valve covers to thoroughly clean the parts- mostly the throttle body, to try to fix the idle choppyness. I used carb cleaner to remove the carbon from the TB and an engine cleaner/degreaser to attempt to remove as much deposit that I could from the intake manifold. I did not disconnect the electrical unit from the trottle body b/c I read previoulsy that it needs to be finely adjusted for proper idling. I did remove the electrical unit from the intake manifold body to clean the hell outta the inside along with some deposit on the electrical unit.:ugh3: During disassembly a small amount of antifreeze dripped from a hose onto or around the distributor. Also on the rear valve cover there is a 'green electrical plug with a black plastic connected tube on the side of it' in that two hoses connect to that I broke (cracked the black plastic from the side and reconnected with glue-seemed functional??). Overall I reassembled everything to its exact and proper fitting only to find that it will NOT start. It cranks perfect but will not fire. I have read several posts on this forum and have found some things I may diagnose tomorrow-like plug wires firing; fuel pump functioning;fuel injectors working- but nothing seems to fit my problem, plus I need my car running to diagnose problems. I also put in a new fram air filter. In addition there are four small hoses that run side by side from the intake manifold near the throttle body into two seperate green colored plugs each with two nipples that the hoses connect with; on one of those green plugs both nipples have cracked off and the hoses are no longer attached with the plug-only with the intake manifold- what does this control? Please give some insight to what you think I might be dealing with here. :confused: THANKS!!:D
 

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O My!

Ok first the "green plugs w/ the broken nipples." Those are the BVSV for the the EGR and the EVAP. the left one connects to the EGR, the right to the EVAP siystem. having either of those broken will cause a CEL

When you changed your plugs, did you change them one at a time? or simultaneously. Did you also change the Spark plug wires and the distributor cap and rotor?

If you also changed the spark plug wires and distributor cap, there's a good chance you changed the firing order.

You mentioned you disassembled the Intake manifold. Did you use the old gasket, or did you replace it with a new one. If you changed out ur gasket, you may not have completely removed the old gasket causing a vacuum leak in the system:

http://www.youtube.com/watch?v=2pU50nAwJmw
*TURN DOWN YOUR SPEAKER VOLUME; VIDEO IS LOUD*

That's what happened after i did my spark plugs. Is that similar to what's happening to you?
 

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Lexuszeal
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6 Posts
Discussion Starter #3
I am new to the site and unfamiliar with abbreviations... so i broke the 'BVSV' on the left to the 'EGR'. This is causing what is called "CEL"?

Also I changed only the spark plugs not the wires or distributor cap/rotor. I used the old gasket for the intake manifold. However I am unsure which gasket you are refering to because i used the old gasket between the TB and Intake and between the plate on the opposite side of the intake held on by six fasteners.. furthermore there was no gasket between the manifold joint.

Today I tried to test for spark by removing the #1 plug wire and using an old spark plug by grounding on the block but could not see any spark. What is the best way to test for spark?
 

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Ok, i reread your original post.

1. you disassembled the intake manifold correct? did you remove the upper intake chamber from the intake manifold? if so, there was a gasket on there; it may be hard as a rock, so you may not have noticed it.

2. your engine turns, but doesn't fire. Did you re-assemble the Cold Start Injector tubes and vacuums properly?

As far as testing for spark, it's been mentioned several times on here and on a couple of my posts. do a search or wait for others to reply. I myself haven't done a spark test.
 

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Lexuszeal
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6 Posts
Discussion Starter #5
Interestingly enough I decided to disassemble everything again--air intake housing; throttle body; intake chamber unit from manifold in order to disassemble the distributor. Once I took off the cap from the distributor I cleaner the rotor copper conductor and all other conductors on the cap; although they were not that dirty they had accumulated minimal corrosion deposit. I went ahead and put everything back together after also recleaning the Idle control valve unit. Once everything was in place I gave it another start and hurray!! It started and ran! The engine idled a little bit better but not perfect. Then what do I decide to do???? readjust the throttle sensor!! I dont know why I did now that I can logically think about it- but I did. Now the engine will start on every third try after minimal adjustment but will only try to idle for less than 30 seconds until it stalls out. I cannot even touch the throttle pedal during this start up time. Now what do I do??? Help!!!:headbang:
 

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Unplug throttle sensor. Try to start the engine. If it runs, the sensor is the problem.
 

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BTW...i never spelled out the acronyms so here it is

BVSV = Bi-metal Vacuum Switching Valve
EGR = Exhaust Gas Recirculation
CEL = Check Engine Light
 

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Lexuszeal
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6 Posts
Discussion Starter #8
Today I removed the throttle body to adjust the throttle sensor. I bought and used an ohm meter to adjust the sensor to specifications. Then reassembled and the same symptoms remained. I will start the car and it will only run for a short time before it dies again. Funny thing is that when I disconnect the plug that connects to the air intake the car will stay running @ idle speed but I cannot open the throttle. Maybe someone can help me diagnose this issue. Thanks!!
 

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Lexuszeal
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6 Posts
Discussion Starter #10
Yes. When I unplug the air mass flow sensor from the intake box the car runs fine for however long until I push the gas. What does this indicate that is wrong when I do have it plugged in? I cannot unplug the throttle sensor and keep it running; I cannot have the mass air flow sensor in and keep it running.....
 

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VeeZed
1988 Toyota Camry V6
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2,298 Posts
Motor should not start with the AFM disconnected...since it controls when to engage the fuel pump. If it does, sounds like a wiring problem almost...a short somewhere perhaps.
Reason it stalls out when you throttle up with the AFM disconnected is because there is no metering device to control the amount of fuel. It will run completely rich or lean (cant remember which way the resistance goes)..and yeah, cut out.
Check continuity across the wiring harness to the ECU from the AFM and check the ECU resistance. (details of correct values in a good workshop manual).
The car also should not run with the throttle sensor unplugged as it has an idle switch which controls the engine idle settings...so that part is working correctly atleast.
 
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