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1dodge1mopar
User
Oct 26, 2009, 11:25 AM
Post #1 of 9
(3544 views)
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I HAVE A '93 BLAZER S-10 4X4 AUTO W/OD. IT HAD A "Z" ENGINE IN IT. I HAD A USED 4.3 MFI PUT IN. FOR THE LAST 2 YRS, IT HAS GIVEN ME QUALITY PERFORMANCE. IN THE LAST 2 WEEKS, IT HAS COME TO THIS : 1) ROUGH IDLE BUT WILL ACT FINE W/THROTTLE UP, 2) WHEN ON ROAD, WILL ACCELERATE DESCENTLY, WITH TIMES OF STAYING LONGER IN ONE GEAR THEN, SOMETIMES SHIFTING "HARD" INTO NEXT GEAR. AROUND 60MPH, I WILL GET A "KICK-DOWN" AND IF I ACCELERATE MORE, IT WILL "KICK-DOWN" EVEN LOWER AND IF I PUT MY "FOOT IN IT", IT WILL START TO "BACK FIRE" AND 3) WHEN COMING TO A STOP OR JUST STARTING UP, I LOSE BRAKE ASSIST.
FROM MY EXPERIENCE, I AM SURE IT IS A VACUMN PROBLEM. I HAVE CHANGED (INSTALL NEW) EGR VALVE AND CHECKED PERFORMANCE-NO CHANGE. I HAVE CHECKED THE TPS VOLTAGE VALUES (.59 V-CLOSED THROTTLE, 4.57 V-WIDE OPEN THROTTLE-KEY ON, ENGINE NOT RUNNING, WITH A SLOW INCREASE IN V'GE AS THROTTLE OPENED. I HAVE
DONE SOME RESEARCH IN MY CHILTON MANUAL AND ONLINE WITH NO REAL SOLUTION.
THE ONE THING THAT I NOTICED IS THAT AT 60 MPH, KICK DOWN, BACK OFF THROTTLE, GO DOWN HILL, INCREASE THROTTLE SLOWLY, PICK UP MORE SPEED-BLAZER TRAVELING AT ESTIMATE OF ABOUT 70 MPH, WILL KICK DOWN TWICE QUICKLY AND SPEEDOMETER STILL REGISTERING JUST A HAIR OVER 60 MPH @ KICK DOWN AND SPEEDOMETER WILL GO "BACKWARDS" TO, SOMETIMES, BELOW 50 MPH!! HOW CAN THIS BE?
KNOWING THIS, I , USING MY COMMON SENSE, RELATE THIS PROBLEM TO A "SPEED SENSOR"-WHICH THE CHILTON MANUAL MENTIONS BUT, DOES NOT GO INTO DETAIL AS TO 1) LOCATION, 2) PROBLEMS OCCURING WITH A BAD MODULE OR 3) TROUBLESHOOTING TECHNIQUES TO ISOLATE A POSSIBLE PROBLEM WITH IT.
WHAT CAN BE THE SOURCE OF VACUMN LOSS? NOTHING HAS CHANGED DRAMATICALLY WITH ANYTHING ENGINE-WISE. WHEN I STARTED HAVING ROUGH IDLING AND ACCELERATION PROBLEMS, I PULLED THE DIST CAP AND ROTOR AND REPLACE WITH NEW (LIFETIME PRODUCTS)-NO CHANGE IN PERFORMANCE-SAME PROBLEM.
I KNOW THE ECM GETS INPUT FROM ALL THE SENSORS TO REGULATE THE TIMING, THE GAS MIXTURE AND VOLTAGE.
DO I HAVE A SPEED SENSOR PROBLEM HERE, A BAD ECM PROBLEM OR SOMETHING ELSE I AM MISSING?
DOES ANYONE HAVE A HANDLE ON THIS? ANY SUGGESTIONS WILL BE USED TO ELIMINATE MY PROBLEM.
THNAX FOR LISTENING.
ED BASS
BOONE, IOWA
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 26, 2009, 11:40 AM
Post #2 of 9
(3537 views)
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Re: VACUMN PROBLEM
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Your on the wrong track here.
Do this......
Drop your exhaust pipe at the manifold and test drive it like that making sure there are no wires in peril of burning. If it runs a lot better, replace the Catalytic Converter because it's plugged up.
If you have the means to take a pressure test on the exhaust, you could avoid removing it.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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1dodge1mopar
User
Oct 26, 2009, 12:09 PM
Post #3 of 9
(3531 views)
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Re: VACUMN PROBLEM
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THE CAT CONVERTER HAS BEEN OFF (DON'T TELL THE GOV'T!) FOR ABOUT A YEAR NOW. I HAD A MECHANIC TELL ME TO DO THIS WHEN THE ORIGINAL ENGINE WAS ACTING UP-DOING JUST ABOUT THE SAME THING. HE SAID MOST PERFORMANCE PROBLEMS OCCUR BECAUSE OF THE CC.
COULD THERE BE A SIMILAR PROBLEM ELSEWHERE? RIGHT WHEN I REMOVED THE CC, I NOTICED THE MUFFLER HAD A SIZABLE HOLE IN IT AND WENT AHEAD AND REPLACED IT THEN AS I WAS UNDER THE VEHICLE TO SAVE "DOWN THE ROAD" REPAIRS.
THE 3 AREAS I HAVE SUSPECT WITH ARE 1) ECM, 2) MAP SENSOR, AND 3) IGNITION MODULE ON THE DIST.
WHAT ARE YOUR SUGGESTIONS?
THANX FOR LISTENING.
ED BASS
BOONE, IOWA
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 26, 2009, 12:16 PM
Post #4 of 9
(3528 views)
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Re: VACUMN PROBLEM
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I still think you need to check for a plugged exhaust. You also need to actually take a vacuum reading to determine just what the vacuum is doing.
PS, drop the caps. That's considered yelling in here.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Oct 26, 2009, 12:17 PM)
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Loren Champlain Sr
Veteran
/ Moderator
Oct 26, 2009, 4:36 PM
Post #5 of 9
(3515 views)
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Re: VACUMN PROBLEM
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Ed;
The shifting and speedometer issues, to me, point to a VSS problem. But, it sounds as if other problems may exist, also.
The hesitation could be TPS. Sweeping the TPS very slowly with an ohmmeter, watch for 'glitches'. Using a vacuum guage, measure manifold vacuum at an idle. It should be steady, around 17hG or more. Raise the engine rpm to 2500 and take another reading. It should be as great or greater than the reading was at idle. A more accurate test would be as HT suggested. Remove the oxygen sensor and install a pressure guage. If you have more than 2psi, the exhaust is restricted. I would like to see fuel pressure readings and any trouble codes that have been stored, also.
You mentioned 'rough idle'. The manifold vacuum is directly affected by the way the engine runs. If it is running poorly, the manifold vacuum will be low. This problem must be corrected first.
Loren
SW Washington
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1dodge1mopar
User
Oct 26, 2009, 6:12 PM
Post #6 of 9
(3512 views)
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Re: VACUMN PROBLEM
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THE LAST CHECK ON DTC, IT SHOWED 1) 22-TPS, 2) 23-MAT (THIS CODE IS NOT LISTED FOR THE 1993 4.3 MFI-IT IS LISTED FOR THE 88-92 ENGINES (EXCEPT MFI-TURBO), 3) 32-EGR SYSTEM, AND 4)34-MAP SENSOR CIRCUIT (LOW-HIGH VACUMN).
sorry about the caps people! i forgot!
the map system sounded most plausable but, the vss also could be a plausable root cause. i am not a rich person. i am a "shade-tree" mechanic who starts with the cheapest part in a suspected system 1st. when i was having rough performance with my isuzu rodeo, i did some reading, replaced the water temp sensor for $4.68 and solved the problem.
"my" system does work.
i will start with dropping the exhaust pipe off the exh man and run it to see if that changes anything. i will then change the wts next, then, the cheaper of the map sensor ($92-oreilly's) or the vss.
i just put the muffler on about this time last year. it could have rusted enough (with the unseasonable weather we have had this year) to cause a restriction, thereby, causing the problem.
thanx for your help. i will get back to you with the solution when i find it.
thanx for listening.
ed bass
boone, iowa
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 26, 2009, 6:16 PM
Post #7 of 9
(3509 views)
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Re: VACUMN PROBLEM
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A plugged exhaust will lower your vacuum, reduce your brake boost and cut vacuum to the MAP so that could account for a lot of your symptoms.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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1dodge1mopar
User
Oct 28, 2009, 9:33 AM
Post #8 of 9
(3493 views)
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Re: VACUMN PROBLEM
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i disconnected the exhaust right off the header, before the muffler and test drove it. after dropping the ex-pipe, the engine didn't hardly want to run at all. it went from bad to worse with the pipe off. i have put it back on and it won't
hardly idle. it has died on me at a stop 4-5 times. i had disconnected the IAC valve before and the idle was higher and
more steady but, that doesn't help now.
once again, the DTC codes that displayed were: 1) 22-TPS, 2)23-MAT (not a code for '93 mfi), 3)32-EGR, 4) 34-MAP. I
have tried a new egr valve-that didn't help idle or brake assist. the OREILLY salesman said my problem sounded like
a bad EGR valve. i also understand that other sensors are related to the correct functioning of the EGR valve. i now wonder if more than one sensor/valve could be causing the "whole" problem.
with the exhaust off, the blazer exibited the same speed "mood"-when the indicator on the speedometer reached 60 mph, it would still "kick" down from od to d and, if pushed faster, down to 2nd with the indicator going "backwards" to
below 50 mph a couple times. this problem leads me to believe it could be the VSS. what i don't understand is if the VSS
being bad can affect the vacumn supply.
i went into my local OREILLY website with my vehicle information. it shows a BWD "EGR vacumn control solenoid" listed for my s-10 4 x4 "w" engine. the only problem i have with this part, is that i cannot find it anywhere on the "top side" of the engine. do all the 4.3 mfi "w" engines have this part. it sounds reasonable that a "bad vacumn control solenoid" could be causing the problems i am experiencing with my s-10.
as i have said before, i am not a rich guy and i try not to buy parts i don't need to keep my vehicle running well. a vss is $96 and an egr VCS IS $68. i just spent $235 for an EGR valve i can't return now. i had it on the engine for about 30 secs to check if it improved idle and gave me vacumn brake assist-it didn't. OREILLY tells me i cannot return an "installed"
part. as you can see, i am desperately trying to get the right info to replace the problem part.
i know that auto mechanics can be a "hit-n-miss" at times but, i am unemployed and "desperate".
any advice will be muchly appreciated. advice already given has been tried with the tools i have at my disposal-no vacumn guage, no exhaust pressure guage, no sensor tester. i just have a multitester and hand tools and a pc. of wire for the dtc test.
thanx for listening.
ed bass
boone, iowa
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Loren Champlain Sr
Veteran
/ Moderator
Oct 28, 2009, 10:37 AM
Post #9 of 9
(3489 views)
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Re: VACUMN PROBLEM
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Ed; Don't waste your money on the sensor. The only time the EGR will give you a problem is if it is stuck open. It really does sound as if you've got more than one thing going on here. As far as the EGR valve goes, I would think that if you talked with the manager, told him that his employee sold you the valve as correcting your problem, that they would take) it back? I can't think of anything other than the VSS (or the circuit) that would cause the speedometer issue. It will affect trans. shifting, but not the other issues. The loss of manifold vacuum will cause the MAP sensor code. Of course, if the MAP is bad, it can cause overfueling which will cause the engine to run poorly and the manifold vacuum to drop. Kind of a 'domino' effect. The TPS can also cause hesitation, surging, eratic trans. shifting, ect. That's why you are going to have to do the testing to determine what is going on. If you don't have the tools to do this, it will probably be cheaper, in the long run, to have a professional diagnose it for you. You can still do the work yourself, once you know what to replace. Guessing can get very expensive, as you have already found out. We'll be happy to help as much as possible, but we need to know the results of the tests that we've suggested. Keep in mind, a trouble code can
can be the result of a totally seperate problem.
Loren
SW Washington
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