Looking for the Doohickie

goatfarmer

goatfarmer

New member
1990 T4r, SR5, auto; within the past week there have been couple occasions where I placed the selector in drive and the engine just shuts down, then it takes some effort to get the engine running, as if it is starving for gas? Once I am able to get the engine running the idle jumps to around 16k rpm, but as it gradually warms-up it drops to the appropriate RPM and the vehicle runs fine after that. If I were to hazard a guess, seems as if it has something to do with a control valve related to engine temperature and some component.

I am pre-70's mechanical experienced; although, I have replaced the T4r CV joints and the entire front and rear suspension; however, when it comes to the engine and transmission, not a clue? I do not have a scanner to diagnose the problem, thought perhaps there is a Doohickie-component I could check to determine if faulty; if so, then replace.

Comments/Suggestions, or Educated Guess appreciated!!.
 
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There's several manuals online for your vehicle, Dave. Search for the links in this forum to the manuals so you can do some of the diagnostics checklists.

I always recommend getting a baseline of information first so you can eliminate all the easy stuff first. Checklist is:


  • Base timing check with connector shorted (shown in the manual)
    Set the TPS correctly.
    Check for codes, if any, search forum for them, most all of them are covered here ad nauseum.
    Pull plugs, check color to see if burning rich or lean, that will tell you more on where to start looking for the problem.


You don't say whether this is a 4 or 6 cylinder, I'm going to assume its the v6, but the above list goes for both engines and will rule out any other issues you may have. It may just fix the problem altogether too!
 
flyinhawaiian01 said:
There's several manuals online for your vehicle, Dave. Search for the links in this forum to the manuals so you can do some of the diagnostics checklists.

Appreciate the information. Recently went thru and replaced majority of the 'tune-up' components for the Smog Inspection and it passed with high marks; having said that, intend going back and recheck.

Since posting the question, I contacted a friend, who gave his daughter the same type vehicle, and borrowed a set of shop manuals. Intend browsing thru the appropriate sections to see if the instructions help in my isolating the problem; if not, likely be less labor intensive if I take the vehicle to the local, and reputable mechanic and have them diagnose and provide a list of item(s) they suspect need to be replaced. Since the vehicle runs fine once it has warmed up I do not believe, or at least hope, it will turn out to be major, seems it should be some type of sensor, control valve, etc.(doohickie), that is faulty. The manual should come in handy in making the repairs?

Again, I thank you for the input!!
Click to expand...
 
Again, 4 or 6 cyl?
4 cyl has an external idle control valve where as a V6 it is built into the throttle body. These doohickies control idle up when cold and readjusts when warmed up.
The TPS also plays a big part in the idle when in park vs drive. Make sure it is adjusted properly.
 
penbergm said:
Again, 4 or 6 cyl?
4 cyl has an external idle control valve where as a V6 it is built into the throttle body. These doohickies control idle up when cold and readjusts when warmed up.
The TPS also plays a big part in the idle when in park vs drive. Make sure it is adjusted properly.
Click to expand...

It is the 6 cylinder. Intend breaking out the manual this eve and review the section on 'idle control valve', and 'TPS', imagine even if I were to replace, it probly requires a special piece of equipment to adjust? Came across website with estimates on the cost for part and labor to replace the TPS, that does not include first diagnosing, certainly can get expensive. I will likely try the 'last resort' method; similar to how I repaired our micro wave; starting the engine, disconnecting a couple hoses to the carburetor, and/or sensors, then liberally spray every orifice associated with the carburetor with carburetor cleaner, I do not expect much, but I did not expect to repair our micro using a similar method with compressed air. One can only hope?

Appreciate the information!!
 
No special tools needed to check the tps. Feeler gauge & meter is all you need. You mention carb? It is fuel injectioned, correct.
 
Its a v6, so it has to be EFI.

Check the section of that manual on testing and setting up the throttle position sensor (TPS), its not hard to do, but it is extremely touchy to get it right. I always suggest just pulling the throttle body off and cleaning it on your workbench, then setting the tps while you have it out. Much easier and you end up with a clean throttle body too.
 
penbergm said:
No special tools needed to check the tps. Feeler gauge & meter is all you need. You mention carb? It is fuel injectioned, correct.
Click to expand...

Yes, it has EFI, I meant the throttle body and the air intake system. Browsed thru the Manual seems the best section to start reviewing would be relating to the EFI, and Air Induction System; which includes the Throttle Body, Throttle Position Sensor, and the Air Valve Operation. (FI-p190) May have to rethink liberally flushing the components and take my time by lightly cleaning using the carb cleaner, and the manual recommends a light brush. Not sure about removing the throttle body, will not decide until I read the section; if need be, I would rather drive the vehicle to the shop than have it towed?

Can not thank U's all for the info, it is very helpful!!
 
Want to thank everyone for their comments and suggestions, I found it very helpful. So far the T4r is now running as it should; I read portions in several sections of the manual so in the event problem resurfaces I should have some inclination where to start? Don't intend returning the shop manual just yet?

Removed the air induction system and thoroughly cleaned; then cleaned the throttle body as best as possible with carb cleaner, checked throttle plate adjustment, but decided before removing, I would try replacing all components necessary for a thorough tune up, at the sales persons advice, added a can of 'sea Foam' motor treatment, and a container of Lucas injector cleaner. Last night, and this a.m. took it out for a test run; not sure, perhaps the issue was 60% tune up, and 40% cleaning and lubricating, the air and throttle body assembly. The oil pressure seems lower than usual, with 210k miles perhaps using too thin motor oil?

Again, I thanks U's for the help!
 
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