'93 limp home case

Chaps3 · 09-18-2009, 09:30 PM

Wife drove the Sidekick home (about ten miles) in limp-home mode yesterday (said it went from great to crap in about ten seconds). This is a '93 16v JX four-door, auto-trans. Car has 160K on od. but is a tow car for motorhome and actually has only about 60K driving miles, still looks and drives like new (until yesterday

)

The situation now is : it will start, run up to about 1500 rpm and then bog down and quit (this with no acelerator applied). Now, if I unplug the MAP and the TBS it starts, idles smoothly, and can run it up as far as I want rpm wise (in other words, regular performance) I have not driven it like this however.

I did put on a new fuel filter and clean the SS EGR lines. The port in the throttle body is clear, as is most of the system as far as I can see.

Unfortunately I removed the neg. battery cable during the filter change so now the original codes are gone. Now I get a 12 (normal) with everything hooked up, and of course a 22 and 34 Map and TBI with them disconnected.

Moving the EGR diaphragm does cause it to stumble and die, as I suspect it should. At least it's not sticking.

So what's the next step? Any advice would be appreciated!

kick-fix · 09-18-2009, 10:51 PM

hi and welcome !
new cap, rotor, wires and plugs then filters. very best first trick.

your map is good, they never fail, save hose to it melting to glue or silly putty.

id first make sure the TPS is calibrated using my tPS page.

the idle switch must be good and set correct.

do obvious and report back,

MAP and the TBS it starts . TPS? mAP ,
there is no map and i bet you mean TPS

is MAP = MAF ( air meter next to air cleaner , you disconnect that)

How to test sensor and actuators
click on TPS.

unpugging the MAF causes mimic mode but ECU would love to use TPS for a better guess on air flow, unpluging both ( fun and thanks for trying) will make ecu work real hard at guessing air flow.

it will use rpm and only to guess at flow. very crude.

kinda amazing it runs. really. Id love to watch..........

Chaps3 · 09-19-2009, 10:28 AM

Great Forum! Yes, I meant the MAF and TPI , should have proof read that a bit better

I was a little tired after slaving over a hot engine all day.

Sounds like some good clues and I will get right on it this morning.

One other little note: After reading your site, I see I should have marked P&Q on the modulator after taking it off and messing with it.
Now, of course, I have no idea how it was originally oriented - any thoughts on that? ...when you buy a new one how do you decide which tube goes where?

Thanks

kick-fix · 09-19-2009, 03:01 PM

no problem , EGR modulator
i have 2 spares maked inside
lid off, filter off
see long pipe pass thru

put oriface down.
Q is on right nipple
see titty boss on right pipe inside, that is Q

cheers.
TPS , throttle postion sensor.

Chaps3 · 09-19-2009, 06:36 PM

No where else could I find that information - many thanks!

Car now starts and runs fine with the MAF, only, unplugged

spray cleaned the MAF today and really thought that would help.

It will idle (low, 300rpm) with everything plugged in but won't really run.

The EGR valve moves fine manually but suppose it could still be clogged up. I will probably pull it and inspect the ports.

I'm no quitter!

I'll be back on it tommorow ( and hopefully with fewer interruptions!) will begin going down the diagnostic list for real.

kick-fix · 09-20-2009, 02:13 AM

No power with MAF connected
plenty with it disconnected.

yes, clean EGR valve seat. so long as it dont leak (or blocked open with carbon chunk your ok for now.

i hope you dont have a bad maf .

Chaps3 · 09-20-2009, 08:53 AM

It looked like new inside when I took it off and spray cleaned it yesterday (CRC MAF Cleaner as you recommended) but of course that doesn't mean it couldn't have an electrical problem.

Thanks for your continued support ! I have a FSM but find your web pages much more understandable, and the inclusion of the little "mechanics tips" are invaluable.

kick-fix · 09-20-2009, 02:46 PM

yes, see my maf page.

it can be tested on car ,

the trick is to get ECU happy enough to make full power then monitor the output the MAF with any voltmeter (its a simple analog linear (almost) level )

the curve is never pubished.

but if you WOT it. it will go to near 4.5vdc.

my theory is to cut the wire to it , just the 1 wire, output.
then attach a meter.
ECU will see its dead, (for sure) and will throw code for it (maybe) and will mimic it (for sure)
this trick which you descovered , allows you to go full power.

Its a limphome mode. of a specific type.
a feature of the ECU code.

then you can monitor the output the MAF and see what it does at idle and up to full load.
run a wire to the passenger set to this node.

see last drawing with red words

Howto-test-a-MAF

this is a chicken and egg test.

maf must work to get a good reading.
see? so we go to mimic mode and then get power and then get a real reading with huge volumes of air flowing.

cheers.

Chaps3 · 09-20-2009, 02:56 PM

It 's ports were very clean, BUT the bolts were little more than finger tight and the gasket was loose and just fell apart when I took the valve off. I could see that it had been leaking air. I put on a new gasket and torqued the bolts down - still won't run with the MAF plugged in. I'm wondering if the EGR leaking air for some time could cause a problem with the MAF. Will start testing the MAF as soon as it quits raining.

Chaps3 · 09-20-2009, 05:14 PM

now, it starts goes up to 1500rpm and bogs down - dies - won't run no matter what sensor plug I pull now

Starting the MAF testing I have 12.6 volts at the battery and only 12.2 volts at the disconnected MAF plug with ignition on. Would this be considered to much of a voltage drop in the wiring?